Methods and devices for applying energy to bodily tissues

ABSTRACT

Devices and methods for treating tissue with microwave energy used in applications such as destroying a soft tissue by microwave ablation and/or creating point, line, area or volumetric lesions. Various embodiments of flexible, low-profile devices are also disclosed where such device can be inserted non-invasively or minimally invasively near or into the target tissue such as cardiac tissue. The devices disclosed herein comprise antennas wherein the field profile generated by an antenna is tailored and optimized for a particular clinical application. The antennas use unique properties of microwaves such as interaction of a microwave field with one or more conductive or non-conductive shaping elements to shape or redistribute the microwave field.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/961,557, filed Apr. 24, 2018 which is a continuation of U.S. patentapplication Ser. No. 12/829,222, filed on Jul. 1, 2010 (U.S. Pat. No.9,980,774) which claims the benefit of U.S. Provisional PatentApplication No. 61/222,409, filed on Jul. 1, 2009 and is acontinuation-in-part of U.S. patent application Ser. No. 12/603,077,filed on Oct. 21, 2009 (U.S. Pat. No. 8,968,287), the contents of whichis incorporated herein by reference in their entireties. U.S. patentapplication Ser. No. 12/603,077 also claims the benefit of U.S.Provisional Patent Application No. 61/222,409, filed on Jul. 1, 2009,61/180,133 filed May 21, 2009, 61/162,241 filed Mar. 20, 2009 and61/107,252 filed Oct. 21, 2008, the contents of which is incorporatedherein by reference in their entireties.

FIELD OF THE INVENTION

This invention relates to medical elements (e.g. microwave ablationantennas), usable for performing diagnostic and/or therapeuticprocedures on or within a patient's body.

BACKGROUND OF THE INVENTION

There is a need for improved devices and methods to treat severalmedical conditions. Several conditions including atrial fibrillation,cancer, Menorrhagia, wrinkles, etc. may be treated by ablating tissue byapplying an ablating energy. Even though devices and methods exist totreat these conditions by ablating tissue, there is still an unmet needfor improved devices and methods.

For example, microwave antennas (e.g. helical antennas) have been usedin medical applications including treatment of benign prostatehyperplasia, cancer treatment, etc. Many of the existing antennas havecommon disadvantages such as device shaft heating and non-uniform lesionprofile along the length of the antenna. Thus there is a need formicrowave antennas that are capable of generating uniquely shapedmicrowave fields that overcome these problems. Several prior artantennas also need cooling mechanisms and sophisticated temperaturemonitoring systems to achieve acceptable clinical results.

Menorrhagia is one of the most common gynecological conditions inpre-menopausal women. It is characterized by excessive menstrual bloodloss. The condition severely affects the quality of life of the affectedwomen since it may interfere with physical activity, work and sexualactivity. Several techniques have been developed that aim to destroy theuterine endometrium to treat menorrhagia in a minimally invasive manner.Such endometrial ablation techniques can be performed by a variety ofmethods such as radiofrequency heating, circulating hot saline in theuterine cavity, microwave heating, cryodestruction, laser destruction,etc. Every current endometrial ablation technique has some fundamentallimitations. For example, the Hydrothermablator™ device by BostonScientific needs a hysteroscope which adds to the procedure cost andcomplexity. Further the device is thick and rigid. Because of that, theprocedure requires significant anesthesia, usually in the form ofconscious sedation or general anesthesia. The Novasure™ device is alsothick and rigid. Thus a significant amount of cervical dilation isneeded to introduce the device into the uterine cavity. Since cervicaldilation is very painful, the procedure requires significant anesthesia,usually in the form of conscious sedation or general anesthesia. Also,the device is expensive (˜$900). Thus, even though there are a varietyof endometrial ablation devices, there is still a need for a small-size,flexible, low-cost, easy to use next-generation device in this large andgrowing market.

Several ablation modalities such as microwave ablation can be used totreat solid tumors (e.g. liver tumors) by heating up the tumor tissue.Devices that use microwave ablation for treating tumors are advantageousover devices that use other ablation modalities because of theirpotential to create larger, uniform volumetric lesions. In prior artmicrowave ablation devices, microwave energy is emitted by an antennaand transmitted to the tumor tissue. The efficacy of the ablationprocedure depends significantly on the power efficiency and the SAR andthermal profile of the antenna. Most existing microwave ablation devicesare derived from the simple monopole antenna and have a linearstructure. Their SAR and thermal profile are substantially ellipticaland they are approximately similar to the shape of a football as shownin FIG. 2E. It is difficult to use a single monopole antenna to ablatetumors that have a thickness or diameter of a few centimeters in asufficiently short time. For many cancer-related applications, thetargeted tumors have an excessive size (e.g. diameter of severalcentimeters) and a single monopole antenna is of limited use. One of thesolutions proposed to increase the lesion size involves using multipleablation devices simultaneously. This increases the complexity of theablation system. The overall size and cost of the ablation device willalso be increased due to more number of elements employed in the system.Also, this increases the invasiveness and complexity of the procedure.

Further, the SAR profile shown in FIG. 2F demonstrates that there is asignificant amount of microwave field proximal to the distal end of thecoaxial cable feeding the radiating element (monopole antenna). Thus theablation will not be accurately contained in the region around theradiating element. A portion of the tissue surrounding the distal regionof the coaxial cable will be ablated. This in turn carries a risk ofdamaging healthy tissue by the microwave energy. Thus there is a needfor improved microwave ablation devices that are low profile and thatcan ablate a tissue volume without damaging adjacent healthy tissue.

Atrial fibrillation (AF) is a cardiac electrophysiological disorderfound in millions of Americans. Various ablation systems, includingcatheters and surgical tools, are used to ablate cardiac tissue to treatatrial fibrillation. In catheter ablation procedures, several individuallesions are then created as part of a desired lesion pattern. In manyexisting procedures, only a single, small, point lesion is created atany given time. Multiple such point lesions are needed to achieve thedesired clinical response in the patient. In such procedures, anelectrophysiologist guides the ablation tip of an ablation catheter to apoint on the left atrium and creates a first point ablation. Once thefirst point ablation is created, the electrophysiologist then guides theablation tip to a new location on the left atrium and creates a secondpoint ablation, typically in communication with the first point lesion.This process continues until the desired lesion pattern is created. Thecreation of such multiple, connecting point lesions is very timeconsuming and technically challenging. There are other limitations topoint ablation systems. For example, during the translation of theablation tip to a new location, the distal ablation tip may slip, orotherwise move across the target tissue in an undesired manner. Thesteps of translation of the ablation tip to a new location are furthercomplicated by the motion of the left atrium because of the naturalbeating of the heart. Further, users of point ablation systems typicallyuse costly support equipment to provide historic and current positioninformation of the ablating portion with respect to anatomical cardiacstructures and previously created lesions. The support equipment isextremely costly and requires additional personnel to operate,ultimately increasing procedure costs. Still another problem with pointablation devices having ablating tip portions is the risk ofperforation. The forces applied to the ablation devices are transmittedby the relatively narrow ablation tip to the atrial wall. Thus therelatively narrow ablation tip exerts a significant amount of pressureon the atrial wall. This in turn may result in perforation of the atrialwall which in turn may lead to formation of a potentially fatalatrio-esophageal fistula. Thus, there is a need for improved ablationdevices that simplify the procedure of catheter ablation for treatingatrial fibrillation and have a low risk of complications.

In order to overcome the limitations of point ablation systems, devicescomprising an array of multiple radiofrequency (RF) electrodes weredeveloped. However, RF electrodes need excellent tissue contactthroughout the length of the electrode(s). This is difficult to achieveusing the prior art delivery systems leading to inconsistent contactbetween the RF electrode(s) and the target tissue. Such inconsistentelectrode contact causes variability in the transmission of energythroughout the target length of ablated coagulated tissue. Thisinconsistency also produces undesirable gaps of viable tissue thatpromote propagation of wavelets that sustain atrial fibrillation, orproduce atrial flutter, atrial tachycardia, or other arrhythmiasubstrate. Thus, there is a need for devices that create sufficientlydeep lesions even without achieving perfect contact with the targettissue.

Thus, even though several methods and devices exist that treat clinicalconditions by energy delivery, there are still unmet needs for improvedmethods and devices.

BRIEF SUMMARY OF THE INVENTION

Several medical applications of the invention for applying energy totarget materials such as tissue are also disclosed herein. Energy may beapplied to tissue to achieve a variety of clinically useful effects.Examples of such effects include, but are not limited to: 1. ablatingtissue to kill or otherwise damage tissue, 2. causing heat-inducedmodification of tissue (e.g. heat shrinkage of collagen), 3. causingheat-induced modification of an artificially introduced material (e.g.heat induced polymerization of an injected monomer), 4. warming tissueto change the metabolic activity of tissue (e.g. warming tissue toincrease the metabolism). 5. causing fat liquefaction e.g. to ease fatextraction during Microwave Assisted

Lipoplasty, 6. causing controlled tissue death to debulk tissue fortreating conditions such as Obstructive Sleep Apnea, BPH, etc. and 7.delivering energy to tissue to change the electrophysiologicalcharacteristics of that tissue.

The present invention discloses devices and methods for treating tissuewith microwave energy. In several method embodiments, microwave energyis used for ablating tissue e.g. for treating atrial fibrillation bycontrolled ablation of left atrial tissue, etc.

The device and methods disclosed herein may be used with or withoutmodifications to create one or more point, linear, area or volumetriclesions. The present invention discloses various embodiments offlexible, low-profile devices that can be inserted non-invasively orminimally invasively into or near the target tissue.

Some of the embodiments herein may be broadly described as microwavedevices comprising a transmission line such as a coaxial cable and anantenna connected to the coaxial cable. The antenna comprises 1. aradiating element, 2. one or more shaping elements and 3. one or moreantenna dielectrics covering one or more portions of the radiatingelement and/or the shaping element. In embodiments wherein transmissionline is a coaxial cable, the radiating element may be a continuation ofthe inner conductor of the coaxial cable or may be an additionalconductive element electrically connected to the inner conductor of thecoaxial cable. The radiating element radiates a microwave field that ischaracteristic of its specific design. The radiated microwave fieldcauses agitation of polarized molecules, such as water molecules, thatare within target tissue. This agitation of polarized moleculesgenerates frictional heat, which in turn raises the temperature of thetarget tissue. Further, the microwave field radiated by the radiatingelement may be shaped or otherwise redistributed by one or more shapingelement(s) in the antenna. In one embodiment, the shaping element(s) aremade of an electrically conductive material (e.g. one or more metallicobjects of various sizes, shapes, orientations, etc.). In thisembodiment, the shaping element(s) may be electrically connected to theouter conductor or shielding element of the transmission line (e.g. theouter conductor of a coaxial cable). In an alternate embodiment, theshaping element(s) are not in direct electrical conduction with theouter conductor or shielding element of the transmission line e.g. theouter conductor of a coaxial cable. The one or more antenna dielectricsmay cover one or more portions of one or both of: radiating element andshaping element. The antenna dielectrics may be used for changing thepropagation of the microwave field from one or both of: radiatingelement and shaping element to the surrounding. The antenna dielectricsmay be used for changing the matching

The one or more additional shaping elements in the antenna may be usedto create a more uniform microwave field distributed over a largerregion. The one or more shaping elements in the antenna may also be usedto improve the power deposition by the antenna. One or both of radiatingelement and shaping element may be enclosed in an antenna dielectricmaterial In several of the embodiments disclosed herein, a conductiveelement (e.g. a length of metallic wire) electrically connected to theouter conductor of a coaxial cable is used to shape the microwave field.

Several embodiments of radiating elements and shaping elements andcombinations thereof are described herein. The shapes of the crosssection of radiating element and shaping element may be designed toachieve the desired mechanical and microwave properties. Examples ofsuch cross section shapes include, but are not limited to round, oval,rectangular, triangular, elliptical, square, etc. Various antennas maybe designed using a combination of a radiating element disclosed hereinand a shaping element disclosed herein. The shape of the microwave fieldemitted by such antennas can be purposely shaped by designing theantenna. For example, an antenna may be designed to generate a microwavefield designed to create a deeper ablation in the center of a targetorgan and shallower ablation towards the periphery of the target organ.

Various embodiments of antenna 104 may be designed to generate a varietyof shapes of SAR and/or the ablation profile. For example, antennas 104may be designed to generate substantially square, triangular,pentagonal, rectangular, round or part round (e.g. half round, quarterround, etc.), spindle-shaped or oval SARs or ablation patterns.

The methods and devices disclosed herein e.g. (a linear antennadisclosed herein) may be navigated through the anatomy and placed at oneor more positions within the target anatomy using one or more steerableor non-steerable devices. Any of the antennas disclosed herein maycomprise one or more attachments or integral elements to enable the userto navigate the antenna through the anatomy. Examples of suchattachments or elements include, but are not limited to: integraltethers or external pull wires to pull one or more regions of a deviceor to bend or deflect one or more regions of a device, internal pullwires adapted to bend or deflect one or more regions of a device, one ormore elements adapted to be steered by a surgical magnetic navigationmodality, etc.

The antennas disclosed herein may be deployed from an insertionconfiguration to a working configuration before being placed in thevicinity or inside of the target tissue. Alternately, the antennas maybe deployed from an insertion configuration to a working configurationafter being placed in the vicinity or inside of the target tissue. Thedeployment of the antennas disclosed herein may be done by one ofseveral methods. The antennas herein may be navigated to the targettissue in a fully deployed configuration. In one embodiment, an antennais navigated to the surface of an abdominal organ e.g. the liver in afully deployed configuration through a laparotomy. In anotherembodiment, an antenna disclosed herein is deployed through anintroducer in which the antenna is in a collapsed, low-profileconfiguration when inside the introducer and is deployed to a workingconfiguration after the antenna exits the introducer. The antenna may bedeployed after the antenna exits the introducer by one or more of: theelastic property of the antenna or its components, the super-elasticproperty of the antenna or its components, the shape memory property ofthe antenna or its components, use of a mechanical deployment mechanismfor the antenna or its components, use of one or more anatomical regionsto change the shape of one or more antenna portions, etc. One or moreportions of the antennas herein may be malleable or plasticallydeformable. This allows the user to shape an antenna to ensure bettercontact with target tissue or better navigation through the anatomy.

The devices disclosed herein comprise antennas wherein the ablationprofile generated by an antenna is tailored and optimized for aparticular clinical application. For example, in the embodiments whereina microwave antenna is used to ablate the entire cavity wall or anentire circumferential region of the cavity wall, the ablation profilemay be designed to ablate substantially the entire cavity wall or anentire circumferential region of the cavity wall without the need forrepositioning of the antenna. In such embodiments, the microwave fieldmay circumferentially envelop the entire antenna. For example, in theembodiments wherein a microwave antenna is used to ablate a tissuevolume, the ablation profile may be designed to ablate substantially theentire tissue volume without requiring repositioning of the antenna. Inseveral device embodiments herein, microwave antennas are designed suchthat they ablate a substantially linear region of tissue. Several suchlinear lesions may be created to form a lesion pattern that achieves thedesired clinical result.

The antennas disclosed herein may be conformable to acquire the shape ofa portion of the target anatomy or otherwise be shaped by one or moreportions of the target anatomy. For example, the antennas disclosedherein may be elastically flexible to conform to the shape of a smallcavity or to the shape of an adjacent wall of the cavity into which theantenna is deployed. The antennas disclosed herein may be sized andshaped to approximate the size and shape of the target anatomy such asthe uterine cavity.

Several embodiments of slim and flexible ablation devices are disclosedherein. This allows the user to introduce such ablation devicesminimally invasively through small incisions or openings or evennon-invasively through natural openings or passageways. Examples ofminimally invasive introduction includes percutaneous introductionthrough the vasculature. Examples of non-invasive introduction includesintroduction from the anus, mouth or nostrils into the gastro-intestinaltract, introduction from the vagina into the female reproductive system,introduction from the urethra into the urinary system, introduction fromthe ear, nostrils or mouth into the ENT system, etc. The devices andmethods disclosed herein may be used to ablate diseased tissue orhealthy tissue or unwanted tissue in organs or artificially createdcavities. The devices disclosed herein may be introduced throughlaparoscopic, thoracoscopic, cystoscopic, hysteroscopic or otherendoscopic openings or instrumentation into or near organs or bodilycavities. The methods disclosed herein may be performed under real-timemonitoring e.g. by using one or more of: direct visual observation,hysteroscopy, cystoscopy, endoscopy, laparoscopy, ultrasound imaging,radiological imaging, etc.

Various additional features may be added to the devices disclosed hereinto confer additional properties to the devices disclosed herein.Examples of such features include, but are not limited to one or morelumens, ability to apply a vacuum or suction to the target anatomy,ability to visualize one or more regions of the target anatomy, abilityto limit the depth of insertion into the target anatomy, ability todeploy the antenna, ability to connect to a source of energy, etc.

Several of the method and device embodiments are designed to minimizethe use of anesthesia such that the methods may potentially be performedusing only local anesthesia.

The dimensions or other working parameters of the devices disclosedherein may be adjustable or programmable based on user inputs. The userinput may be based on factors such as patient's anatomical dataincluding anatomical dimensions and the desired level of safety andefficacy.

The various microwave antennas and the microwave engineering principlesdisclosed herein may be used in a variety of non-medical as well asmedical applications. The near field of the microwave antennas disclosedherein may be used on target materials such as food, industrialproducts, semiconductors, etc. The near field of the microwave antennasdisclosed herein may be used for cooking or heating foods, in industrialprocesses for drying and curing products, in semiconductor processingtechniques to generate plasma for processes such as reactive ion etchingand plasma-enhanced chemical vapor deposition (PECVD).

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A shows a schematic view of an embodiment of a microwave ablationdevice of the present invention having a microwave antenna comprising aradiating element and a microwave field shaping element.

FIG. 1B shows a schematic view of an embodiment of a microwave ablationdevice similar to the embodiment in FIG. 1A wherein a microwave fieldshaping element is connected to a region of the transmission lineproximal to the distal end of the transmission line.

FIG. 1C shows a schematic view of an embodiment of a microwave ablationdevice of the present invention having a microwave antenna comprising aradiating element and a microwave field shaping element.

FIG. 1D shows a transverse section through an embodiment of the coaxialcable of the ablation device of FIG. 1C.

FIG. 1E shows a longitudinal section of the ablation device of FIG. 1Cthrough the distal end of the coaxial cable.

FIGS. 2A and 2B show two side views of a simulated SAR profile generatedby the device embodiment of FIG. 2A.

FIG. 2C shows a top view of a simulated SAR profile generated by thedevice embodiment of FIG. 2A.

FIG. 2D shows the simulated return loss of an ablation device with anantenna of FIG. 2A.

FIGS. 2E and 2F show a side view and the top view respectively of asimulated SAR profile generated by a monopole antenna.

FIG. 2G shows a side view of a simulated SAR profile generated by thedevice embodiment of FIG. 2A without shaping element 114.

FIG. 2H shows the simulated return loss of an ablation device with anantenna of FIG. 2A without shaping element 114.

FIG. 2I shows a photograph of a fully functional, linear antenna similarto the design in

FIG. 2A.

FIG. 2J shows an experimental setup for demonstrating the utility of theantenna of FIG. 2I for intra-cardiac ablation and other applications.

FIGS. 2K-2N show the method steps of a method of creating twooverlapping lesions in a tissue.

FIG. 2O shows a surface view of the two resulting overlapping lesionsobtained from the method in FIGS. 2K-2N.

FIG. 2P shows a view of the section through the plane 2P-2P in FIG. 2Oshowing two deep, overlapping lesions.

FIGS. 2Q and 2R show a uniform lesion created by the antenna in FIG. 2Iin a bent or curved configuration.

FIGS. 3A-3D show embodiments of antenna 104 wherein antenna 104 haslinear, curved, closed loop and helical shapes respectively.

FIG. 3E shows an embodiment of an ablation device comprising a steerableor deflectable antenna.

FIG. 3F shows an embodiment of an ablation device 100 that isrepositioned to ablate multiple target regions.

FIGS. 3G-3H show two configurations of a microwave device having anantenna that can be reversibly converted between a straightconfiguration and a bent configuration.

FIG. 3I shows an embodiment of a method used to create a small,localized “point” lesion on a tissue using the ablation device of FIGS.3G and 3H.

FIG. 3J shows an embodiment of a method used to create a linear lesionon a tissue using the ablation device of FIGS. 3G and 3H.

FIG. 3K shows an embodiment of a method used to create an annular lesionon a tissue using the ablation device of FIGS. 3G and 3H.

FIG. 3L shows an embodiment of a method used to create a round lesion ona tissue using the ablation device of FIGS. 3G and 3H.

FIGS. 4A and 4B show two method embodiments of ablating tissue wherein aradiating element and a shaping element of an antenna are placed onopposite sides of the tissue.

FIGS. 4C and 4D show two method embodiments of ablating tissue locatedbetween an antenna and a shaping element such as a microwave shield orreflector.

FIG. 5A shows an embodiment of a portion of an antenna built on aprinted circuit board.

FIG. 6A shows an embodiment of an ablation device with a radiatingelement and multiple shaping elements adapted to ablate a volume oftissue.

FIGS. 6B and 6C show a side view and a top view respectively of asimulated SAR profile of the embodiment of the antenna of FIG. 6A.

FIGS. 6D and 6E show a side view and a top view of a thermal simulationof the embodiment of the antenna of FIG. 6A.

FIGS. 6F and 6G show a side view and a top view of a simulated SARprofile at 0.915 GHz of an embodiment of an antenna similar to theantenna of FIG. 6A.

FIG. 6H shows the simulated return loss of an ablation device with anantenna of FIGS. 6F and 6G.

FIG. 7A shows an embodiment of a substantially linear antenna used topenetrate a bodily tissue and ablate a tumor.

FIGS. 8A-8D show the steps of a method of minimally invasive treatmentfor treating venous reflux disease.

FIGS. 9A and 9B show a method of transurethral treatment of an internalurethral sphincter for treating stress urinary incontinence (SUI).

FIG. 9C shows a method embodiment of transurethral treatment of aninternal urethral sphincter for treating stress urinary incontinence(SUI) by an energy delivery device cooperating with a positioningelement.

FIG. 9D shows a method embodiment of transurethral treatment of aninternal urethral sphincter for treating stress urinary incontinence(SUI) by an energy delivery device with an antenna that simultaneouslydelivers energy to a larger volume of tissue.

FIG. 10A shows an embodiment of a method for treating Benign ProstaticHyperplasia (BPH) by an energy delivering device.

FIG. 10B shows an embodiment of a method for treating Benign ProstaticHyperplasia (BPH) by an energy delivering device inserted through theurethral lumen.

FIG. 10C shows an embodiment of a method for treating Benign ProstaticHyperplasia (BPH) by an energy delivering device inserted in theurethral lumen.

FIGS. 11A-11C illustrate the use of a microwave device with a steerableor deflectable antenna used to treat Gastroesophageal Reflux Disease(GERD).

FIG. 12A shows a method embodiment of using an antenna along with asurface cooling modality to improve the cosmetic appearance of skin.

FIG. 13A shows a view of an antenna of a microwave ablation deviceoptimized for endometrial ablation.

FIG. 13B shows a section of ablation device 100 of FIG. 13A through thedistal end of coaxial cable 102.

FIG. 14A shows a view of an antenna similar to the antenna of FIG. 13Awithout a center loop.

FIGS. 14B and 14C show the front and side views respectively of the SARprofile generated by an antenna with a center loop similar to theantenna of FIG. 13A.

FIG. 14D shows the simulated return loss of an ablation device with anantenna of FIG. 14B.

FIG. 14E shows the front view of the SAR profile generated by theantenna of FIG. 14B without center loop.

FIG. 14F shows the simulated return loss of an ablation device with theantenna of FIG. 14E.

FIGS. 14G and 14H show the front and side views respectively of the SARprofile generated by an antenna with a center loop similar to theantenna of FIGS. 14B and 14C.

FIGS. 14I and 14J show two alternate embodiments of shapes of microwaveantennas of ablation devices.

FIG. 14K shows the substantially circular crossection of the microwaveantenna of FIGS. 14I and 14J through plane 14K-14K.

FIG. 14L shows two alternate crossections of microwave antenna of FIGS.14I and 14J through plane 14L-14L.

FIGS. 14M-14O show various embodiments of ablation devices comprisingroughly triangular shaped microwave antennas.

FIGS. 14P-14R show various alternate embodiments of center loop.

FIGS. 14S and 14T show two configurations of a mechanically deployableantenna.

FIG. 14U shows a longitudinally un-constrained and laterallyun-collapsed configuration of an embodiment of a microwave antenna.

FIG. 14V shows a longitudinally constrained and laterally un-collapsedworking configuration of the embodiment of a microwave antenna shown inFIG. 14U.

FIG. 14W shows the placement of the microwave antenna of FIGS. 14U and14V in a folded piece of tissue.

FIG. 14X shows the unfolded piece of tissue of FIG. 14W showing theplacement of the microwave antenna of FIGS. 14U and 14V in alongitudinally constrained and laterally un-collapsed workingconfiguration and the ablation obtained from the microwave antenna.

FIG. 14Y shows an unfolded view of ablated tissue after the ablationshown in FIG. 14W.

FIG. 14Z shows a view of the ablated tissue sliced through the plane14Z-14Z in FIG. 14Y.

FIG. 14AA shows a view of the ablated tissue sliced through the plane14AA-14AA in FIG. 14Y.

FIG. 15A shows a view of an antenna of a microwave ablation deviceoptimized for endometrial ablation that comprises a single radiatingelement and two shaping elements.

FIG. 15B shows the placement of the antenna of FIG. 15A between twoopposite tissue surfaces for an ablation procedure and the resultingablation pattern that is obtained.

FIG. 15C shows the reverse surfaces of the tissues of FIG. 15Bdemonstrating transmural lesions.

FIG. 15D-15N illustrate variations of devices having an antenna thatcomprises a single radiating element and one or more shaping elements.

FIGS. 15O-15Q show embodiments of antenna 104 comprising mechanisms toensure proper deployment of antenna 104 in the anatomy.

FIGS. 16A-16D show various views of an embodiment of a shaping elementthat is usable for constraining an antenna to change or constrain theshape of the antenna.

DETAILED DESCRIPTION OF THE INVENTION

This specification discloses multiple antenna designs, systems,structures and devices, and associated methods, which illustrate variousaspects of the invention. The various microwave antennas and themicrowave engineering principles disclosed herein may be used in avariety of non-medical and medical applications. The near field of themicrowave antennas disclosed herein may be used on target materials suchas food, industrial products, semiconductors, etc. The near field of themicrowave antennas disclosed herein may be used for cooking or heatingfoods, in industrial processes for drying and curing products, insemiconductor processing techniques to generate plasma for processessuch as reactive ion etching and plasma-enhanced chemical vapordeposition (PECVD). While these systems, structures and devices, andassociated methods, are discussed primarily in terms of some particularclinical applications (e.g. ablating cardiac tissue to treatarrhythmias, endometrial ablation), the methods and devices disclosedherein are applicable for use in other bodily structures, as well. Thesesystems, structures and devices, and associated methods, may be used forablating tissue in, or adjacent to, the brain, prostate gland, portionsof the urinary tract, gall bladder, uterus and other portions of thefemale reproductive tract, regions of the vasculature, intestines andother portions of the lower alimentary tract, stomach and other portionsof the upper alimentary tract, liver and other digestive organs, lungs,skin, mucus membranes, kidneys, reproductive organs, joints, or otherorgans or soft tissues of the body. The devices and methods disclosedherein may be used for the treatment of knee disorders, anteriorcruciate ligament instability, vertebral disk injuries and chronic lowback pain. The devices and methods disclosed herein may be used severalarthroscopic applications such as shrinking the tissues of theligamentous joint capsule to increase the tension on these ligaments forstabilizing the shoulder joint.

Several devices and methods disclosed herein may be used to treat tissueby microwave thermal ablation. Even though a significant portion of thedisclosure is about microwave device and methods for ablation of tissueto kill or otherwise damage tissue, microwave energy may be applied totissue to achieve a variety of clinically useful effects other thanablation. Examples of such effects include, but are not limited to: 1.causing heat-induced modification of tissue (e.g. heat shrinkage orother alteration in the properties of collagen), 2. causing heat-inducedmodification of an artificially introduced material (e.g. heat inducedpolymerization of an injected monomer), 3. warming tissue to change themetabolic activity of tissue (e.g. warming tissue to increasemetabolism), 4. causing fat liquefaction e.g. to ease fat extractionduring Microwave Assisted Lipoplasty, 5. causing controlled tissue deathto debulk tissue for treating conditions such as Obstructive Sleep Apneaand 6. delivering energy to tissue to change the electrophysiologicalcharacteristics of that tissue. Even though several microwave emittingdevice embodiments herein are called ablation devices 100, suchmicrowave emitting device embodiments may be used for methods that donot involve ablation of tissue.

Microwave thermal ablation does not depend on the conduction ofelectricity to tissue unlike RF ablation. Thus, devices using microwavethermal ablation such as the devices disclosed herein don't need goodcontact with tissue. They can function well even without perfect contactwith the target tissue. Thus, the devices disclosed herein do notrequire extremely precise placement in tissue, thereby reducing thedependence of procedure outcome on physician skills. The devices hereinare designed to have a distal microwave emitting portion comprising anantenna and a proximal shaft. The proximal shaft comprises atransmission line such as a flexible coaxial cable that deliversmicrowave energy from a microwave generator to the microwave emittingportion. The shaft can be designed to be slim (e.g. <3 mm in diameter)to enable the introduction of the ablation device through narrowopenings. The shaft can be designed to be flexible such that minimalforces are exerted on bodily tissues during the introduction of theablation devices into the anatomy. The flexible nature of the shaftenables the shaft to take the natural shape of passage duringintroduction instead of distorting the passage by the shaft of thedevice. For example, when a device is introduced trans-cervically intothe uterus, the shaft may acquire the shape of introduction passagecomprising the vagina, cervical canal and uterine cavity instead ofdistorting one or more of the vagina, cervical canal and uterine cavity.The designs of the coaxial cables disclosed herein confer sufficientflexibility to the device shaft such that the device shaft is capable ofbending by more than 45 degrees when it experiences distorting forces bythe anatomy. If desired, the device shaft may be made stiffer by addingone or more coatings, coverings, stylets and other stiffening elements.

Several of the experiments herein were performed at 0.915 GHz or 2.45GHz ISM band. Antennas, methods, etc. disclosed herein may be used withor without modifications at other frequencies including, but not limitedto ISM bands of 0.433 GHz, 5.8 GHz, etc. The microwave power generatormay be magnetron based or solid state. The microwave power generator maybe single or multi-channel. The microwave power generator used for theexperiments comprised a Vector Network Analyzer (Agilent 8753 series)and amplifier modules build in-house using transistors from FreescaleSemiconductor (Austin, Tex.). The power measurement was made using apower meter (ML2438A Power Meter, Anritsu Company, Richardson, Tex.).Similar devices and components can be used to design the microwavegenerator for clinical use with the devices and methods disclosedherein.

In the experiments, where desired, a fiber optic thermometry system (FOTLab Kit by LumaSense Technologies, Santa Clara, Calif.) was used tomeasure the temperature at several locations in the tissue. The fiberoptic thermometry system was used since it has no metallic componentsthat might interfere with the microwave field. Similar non-interferingthermometry may be used to measure the temperature at one or morelocations during an ablation procedure.

FIG. 1A shows a schematic view of an embodiment of a microwave ablationdevice of the present invention having a microwave antenna comprising aradiating element and a microwave field shaping element. In FIG. 1A,microwave ablation device 100 comprises a transmission line such as acoaxial cable 102. An antenna 104 is connected to the distal end ofcoaxial cable 102. FIG. 1A shows microwave ablation device 100 dividedinto a first zone Z1 and a second zone Z2 by an imaginary transitionline 105. First zone Z1 is proximal to second zone Z2. Transition line105 is defined by the distal end of coaxial cable 102 and issubstantially perpendicular to the axis of coaxial cable 102 at thedistal end of coaxial cable 102. In the embodiment shown in FIG. 1A, thedistal region of coaxial cable 102 lies entirely within first zone Z1and antenna 104 lies entirely within second zone Z2. In a oneembodiment, a single microwave signal is fed to antenna 104 throughcoaxial cable 102. Antenna 104 generates a microwave field. The nearfield of the microwave field generated by antenna 104 may be used fortissue ablation.

In FIG. 1A, antenna 104 comprises a radiating element 112 and a shapingelement 114. Radiating element 112 may be made of a variety ofconducting materials e.g. metals, conductive polymers, materials withembedded conductive particles, etc. When microwave energy is deliveredthrough coaxial cable 102 to antenna 104, a first microwave field isemitted by radiating element 112. The first microwave field interactswith shaping element 114. This interaction induces a leakage current onshaping element 114. The leakage current in turn creates a secondmicrowave field. The first microwave field and the second microwavefield together combine to produce a unique shaped microwave field ofantenna 104 that is clinically more useful that the unshaped microwavefield generated by an antenna 104 comprising only radiating element 112.Thus the original microwave field is redistributed by the design ofshaping element 114. Shaping element 114 alone is not capable offunctioning as an antenna; rather shaping element 114 shapes orredistributes the electromagnetic or microwave field emitted byradiating element 112 to produce a clinically improved microwave field.It should be noted that there is no direct electrical conduction betweenradiating element 112 and shaping element 114. Antenna 104 furthercomprises one or more antenna dielectrics 116 covering one or moreportions of one or both of: radiating element 112 and shaping element114. In FIG. 1A, an antenna dielectric 116 covers the proximal portionof radiating element 112. Any of the antenna dielectrics 116 disclosedherein may be used to shape the microwave field and to optimize theperformance of antenna 104. Any of the antenna dielectrics 116 disclosedherein may be replaced by one or more conducting polymers.

A microwave field couples to the nearest conductive path. In prior artmonopole antennas such as shown in FIG. 2E, the nearest conductive pathis provided by the shielding element of the transmission line (e.g. theouter conductor 106 of the feeding coaxial cable 102). This causes astrong concentration of the microwave field in the junction betweenantenna 104 and transmission line 102. However, in several embodimentsof antenna 104 disclosed herein, the nearest conductive path is providedby shaping element 114. Thus the microwave field couples to shapingelement 114 instead of coupling to the shielding element of thetransmission line (e.g. the outer conductor 106 of the feeding coaxialcable 102). Therefore, minimal microwave field is coupled proximally tothe shielding element of the transmission line. This in turn creates aunique, shaped or redistributed microwave field that does notsignificantly extend proximally to antenna 104 as shown in FIGS. 2A, 2M,6B, 6F and 14B. Further, the combination of radiating element 112 andshaping element 114 improves the power deposition of antenna 104.

Antennas disclosed herein may comprise one or more shaping elements 114made of a variety of conducting materials e.g. metals, conductivepolymers, materials with embedded conductive particles, etc. Suchshaping elements 114 may comprise one or more dielectrics layers toinsulate the shaping element 114 from surrounding tissue. Examples ofsuch shaping elements 114 include, but are not limited to: straight orcurved segments of metallic elements, elements with a circular or ovalshape, elements with a polygonal shape (e.g. triangular, square,rectangular, pentagonal, etc.), multiple elements joined together by oneor more electrically conducting joint(s), multiple elements joinedtogether by a non-electrically conducting joint(s), elements withmultiple curves, symmetrically arranged segments of elements,non-symmetrically arranged segments of elements, etc.

In the embodiment shown in FIG. 1A, the width of antenna 104 issubstantially greater that the width of the coaxial cable 102. In oneembodiment, radiating element 112 is a continuation of the innerconductor 108 of a coaxial cable 102. In a one embodiment, shapingelement 114 is made of an electrically conductive material e.g. a metaland is electrically connected to a region of outer conductor 106 ofcoaxial cable 102. In an alternate embodiment, antenna 104 comprises oneor more conductive shaping elements 114 that are electrically isolatedfrom outer conductor 106. In this embodiment, one or more shapingelements 114 function as passive radiators or parasitic elements ofantenna 104. In one embodiment, shaping element 114 is designed to actas a microwave shielding element and/or a microwave reflecting element.

Embodiments of antenna 104 may be designed wherein radiating element 112has no sharp corners. Sharp corners in radiating element 112 may causethe field to concentrate in the vicinity of the sharp corners. Thusembodiments of the present invention may be designed that have minimalor no sharp corners to avoid undesirable regions of concentratedmicrowave field.

Antenna 104 may be designed to have a shape that substantiallyapproximates the shape of the target tissue to be ablated. In oneembodiment, antenna 104 has a roughly triangular shape that isespecially suited for endometrial ablation. In another embodiment,antenna 104 has a roughly linear shape that is especially suited for theablation of a linear region of tissue e.g. for the creation of a linearlesion in the left atrium.

Further, antenna 104 may be designed to be sufficiently flexible suchthat during and after introduction and deployment of antenna 104 in theanatomy, the anatomy experiences only slight forces from antenna 104.This may be achieved by designing an antenna 104 comprising one or moreflexible radiating elements 112, one or more flexible shaping elements114 and one or more flexible antenna dielectric materials. Sufficientlyflexible antennas may reduce damage to healthy tissue as well aspotentially reduce the pain experienced by the patient during theintroduction and deployment. Antenna 104 may be introduced in acollapsed configuration through a small lumen. The collapsedconfiguration lowers the overall profile of antenna 104. In thecollapsed configuration, radiating element 112 and shaping element 114may be closer to each other than in the non-collapsed configuration.This enables the introduction of antenna 104 through narrow catheters,shafts, introducers and other introducing devices. Further, this enablesthe introduction of antenna 104 through small natural or artificiallycreated openings in the body. Further, antenna 104 may be designed tohave an atraumatic distal end in which the distal region of antenna 104is wider and/or sufficiently flexible to reduce the risk of perforationof tissue. The flexible nature of antenna 104 enables antenna 104 totake the natural shape of an introduction passage during introductioninstead of distorting the passage. For example, when antenna 104 isintroduced via the vasculature into a heart chamber via a femoral veinaccess, flexible antenna 104 may be easily introduced through theintroduction passage comprising the femoral vein access site, femoralvein and the inferior vena cava.

In one embodiment, the length of radiating element 112 measured alongthe radiating element 112 from the distal end of coaxial cable 102 orother transmission line until the distal end of radiating element 112 isan odd multiple of one quarter of the effective wavelength at one of:433 MHz ISM band, 915 MHz ISM band, 2.45 GHz ISM band and 5.8 GHz ISMband. For example, the length of radiating element 112 may be threequarters of the effective wavelength at the 915 MHz ISM band. Theeffective wavelength is dependent on the medium surrounding the antennaand the design of a dielectric covering on the radiating element 112.The design of the dielectric covering includes features such as the typeof dielectric(s) and thickness of the dielectric layer(s). The exactlength of the radiating element 112 may be designed to get goodimpedance matching.

In any of the embodiments herein, the proximal portion of radiatingelement 112 may be a continuation of the inner conductor 108 of coaxialcable 102. The proximal portion of radiating element 112 in any of theembodiments herein may be designed to be stiffer and have a greatermechanical strength than the distal portion of radiating element 112. Inone such embodiment, radiating element 112 is a continuation of innerconductor 108 of coaxial cable 102 and dielectric material 110 ofcoaxial cable 102 is retained on the proximal portion of radiatingelement 112. In another embodiment, the proximal portion of radiatingelement 112 is made stiffer by coating the proximal portion of radiatingelement 112 by a layer of dielectric.

In any of the embodiments herein, one or more outer surfaces ofradiating element 112 may be covered with one or more layers of antennadielectrics 116. The thickness and type of antenna dielectrics 116 alongthe length of radiating element 112 may be designed to modify andoptimize the microwave properties of the antenna 104. For example, oneor more antenna dielectrics 116 covering radiating element 112 may beused to shape the microwave field and to optimize the performance ofantenna 104. The one or more antenna dielectrics 116 covering radiatingelement 112 may be used to shape the microwave field by changing thelocal dielectric environment in the region adjacent to radiating element112. In any of the embodiments herein, every portion of radiatingelement 112 may be covered with some antenna dielectric 116 such that nometallic surface of radiating element 112 is exposed to tissue. Thus,radiating element 112 may be electrically insulated from tissue. Thus,in such embodiments, radiating element 112 is able to transmit amicrowave field into tissue, but unable to conduct electricity totissue. Thus, in such embodiments, there is no electrical conduction andno conductive path between radiating element 112 and shaping element114. Further, in such embodiments, there is no electrical conduction andno conductive path between radiating element 112 and the surroundingtissue. Examples of dielectric materials that can be used to design oneor more embodiments disclosed herein include, but are not limited toEPTFE, PTFE, FEP and other floropolymers, Silicone, Air, PEEK,polyimides, cyanoacrylates, epoxies, conducnatural or artificial rubbersand combinations thereof. In one embodiment, the dielectric on aproximal portion of radiating element 112 is a continuation of thedielectric 110 of coaxial cable 102. The thickness of a dielectric onradiating element 112 may vary along the length of radiating element112. Further, the crossection of a dielectric on radiating element 112may not be radially symmetric. The various configurations of thedielectric may be designed to achieve a desired ablation profile as wellas achieve a desired impedance matching or power efficiency. In oneembodiment, entire radiating element 112 is covered with a siliconedielectric. The layer of silicone used to coat a distal portion ofradiating element 112 may be thinner than the layer of silicone used tocoat a proximal portion of radiating element 112. The thinner siliconedielectric may be used to compensate for the lower field strength thatnormally exists at the distal portion of a microwave antenna. Thus, themicrowave field is made more uniform along the length of radiatingelement 112. In one device embodiment with a silicone dielectric aroundradiating element 112, radiating element 112 is made of a metallicmaterial and the circumference of the metallic material of a distalregion of radiating element 112 is more than the circumference of themetallic material of a proximal portion of radiating element 112. Thiscauses the silicone dielectric to stretch more at the distal portionthan at the proximal portion of radiating element 112. This in turngenerates a thinner layer of dielectric at the distal portion ofradiating element 112 than at the proximal portion of radiating element112. In another embodiment, entire radiating element 112 is made from asingle length of metallic wire of a uniform crossection. In thisembodiment, a tubular piece of silicone dielectric of varying thicknessmay be used to cover radiating element 112. The tubular siliconedielectric is used to cover radiating element 112 such that the layer ofsilicone dielectric is thinner around a distal portion and thickeraround a proximal portion of radiating element 112.

In any of the embodiments herein, the shape of radiating element 112 maybe that same or different from the shape of shaping element 114. Furtherin any of the embodiments herein, both radiating element 112 and shapingelement 114 may be non-linear. Further, in any of the embodimentsherein, radiating element 112 and shaping element 114 may benon-parallel to each other.

FIG. 1B shows a schematic view of an embodiment of a microwave ablationdevice similar to the embodiment in FIG. 1A wherein a microwave fieldshaping element is connected to a region of the transmission lineproximal to the distal end of the transmission line. This embodimentdiffers from the embodiment in FIG. 1A since in FIG. 1A, shaping element114 is connected to the distal end of the transmission line. In oneembodiment of the device shown in FIG. 1B, shaping element 114 ismetallic and is electrically connected to a region of outer conductor106 of coaxial cable 102.

In FIGS. 1A and 1B, since radiating element 112 is in electrical contactwith inner conductor 108, there is a first electrically conductive pathextending from inner conductor 108 till the distal end of radiatingelement 112. In the embodiments wherein shaping element 114 is made of aconductive material and is electrically connected to outer conductor 106of coaxial cable 102 or other transmission line, there is a secondelectrically conductive path extending from outer conductor 106 till thedistal end of shaping element 114. In such embodiments, even thoughthere are two conductive paths that extend from first zone Z1 to thesecond zone Z2, the designs, materials and the microwave properties ofthe two conductive paths may be significantly different in first zone Z1and second zone Z2. For example, the region of the first conductive pathin first zone Z1 is surrounded by the dielectric 110 of coaxial cable102 whereas the region of the first conductive path in second zone Z2may be surrounded by one or more dielectric materials or by ananatomical region such as the target tissue. Further, in FIGS. 1A and1B, the microwave field in first zone Z1 is substantially confinedbetween inner conductor 108 and outer conductor 106 of coaxial cable102. However, in second zone Z2, the microwave field is non-confinedbetween radiating element 112 and shaping element 114. Further, in firstzone Z1, outer conductor 106 of coaxial cable 102 is locatedsymmetrically around inner conductor 108 and at a substantially constantdistance from inner conductor 108. However, in second zone Z2, radiatingelement 112 and shaping element 114 are not located symmetricallyrelative to each other and the distance between radiating element 112and shaping element 114 may or may not be constant throughout secondzone Z2. Further, outer conductor 106 of coaxial cable 102 is orientedparallel to inner conductor 108 in first zone Z1. But in second zone Z2,radiating element 112 and shaping element 114 may or may not be parallelto each other. However, radiating element 112 and shaping element 114may both have planar shapes. In one such embodiment, a plane containingradiating element 112 is substantially parallel to a plane containingshaping element 114. In first zone Z1, outer conductor 106 of coaxialcable 102 always acts as a shield for the microwave field in first zoneZ1 whereas in second zone Z2, shaping element 114 may or may not act asa shield for the microwave field in second zone Z2. In first zone Z1,the distance between outer conductor 106 and inner conductor 108 may besubstantially less than a distance between radiating element 112 andshaping element 114 in second zone Z2.

FIG. 1C shows a side view of an embodiment of a linear microwave antennaof the present invention having a microwave antenna comprising aradiating element and a microwave field shaping element. In theembodiment shown in FIG. 1C, the novel microwave field shaping techniqueof the present invention is used to improve the performance of a helicalantenna. The resultant antenna can be used to create a uniform lesionalong the length of the antenna without adversely affecting tissuessurrounding the transmission line. In FIG. 1C, microwave ablation device100 comprises a transmission line such as a coaxial cable 102. Anantenna 104 is connected to the distal end of coaxial cable 102. In theembodiment shown in FIG. 1C, the width of antenna 104 is substantiallythe same as the width of the coaxial cable 102. FIG. 1C shows microwaveablation device 100 divided into a first zone Z1 and a second zone Z2 byan imaginary transition line 105. First zone Z1 is proximal to secondzone Z2. Transition line 105 in FIG. 1C is defined by the distal end ofcoaxial cable 102 and is substantially perpendicular to the axis ofcoaxial cable 102 at the distal end of coaxial cable 102. In theembodiment shown in FIG. 1C, the distal region of coaxial cable 102 liesentirely within first zone Z1 and antenna 104 lies entirely withinsecond zone Z2. In one embodiment, a single microwave signal is fed toantenna 104 through coaxial cable 102. Antenna 104 generates a microwavefield. The near field of the microwave field generated by antenna 104may be used for achieving the desired clinical outcome such as ablatingtissue. In FIG. 1C, antenna 104 comprises a radiating element 112 and ashaping element 114. In one embodiment, radiating element 112 is acontinuation of the inner conductor 108 of coaxial cable 102. Shapingelement 114 shapes the microwave field emitted by radiating element 112.In one embodiment, shaping element 114 is made of an electricallyconductive material e.g. a metal or a conductive polymer and iselectrically connected to a region of outer conductor 106 of coaxialcable 102. In an alternate embodiment, a conductive shaping element 114is electrically isolated from outer conductor 106. In this embodiment,shaping element 114 functions as a passive radiator or parasitic elementof antenna 104. Shaping element 114 in this electrically isolatedembodiment absorbs microwaves radiated from radiating element 112 andre-radiates microwaves. It should be noted that there is no directelectrical conduction between radiating element 112 and shaping element114. When microwave energy is delivered through coaxial cable 102 toantenna 104 in FIG. 1C, a first microwave field is emitted by radiatingelement 112. This first microwave field is a normal mode microwave fieldof a small diameter (antenna diameter D is much less than microwavewavelength) helical antenna. The first microwave field interacts withshaping element 114. This interaction induces a leakage current onshaping element 114. The leakage current in turn creates a secondmicrowave field. The second microwave field is an elongated, axial modemicrowave field due to the elongate shape of shaping element 114. Thefirst microwave field and the second microwave field together combine toproduce a unique shaped microwave field of antenna 104 that isclinically more useful that the unshaped microwave field generated by anantenna 104 comprising only radiating element 112. Thus the originalmicrowave field is redistributed by the design of shaping element 114.Shaping element 114 alone is not capable of functioning as an antenna;rather shaping element 114 shapes or redistributes the electromagneticor microwave field emitted by radiating element 112 to produce aclinically improved microwave field. It should be noted that there is nodirect electrical conduction between radiating element 112 and shapingelement 114 in FIG. 1C.

Further, the specific design of shaping element 114 may be used toimprove the power deposition of an antenna 104 comprising radiatingelement 112. Shaping element 114 may be made of one or morenon-insulated or insulated elements. Examples of such elements include,but are not limited to: straight or curved segments of metallicelements, elements with a circular or oval shape, elements with apolygonal shape (e.g. triangular, square, rectangular, pentagonal,etc.), multiple elements joined together by an electrically conductingjoint(s), multiple elements joined together by a non-electricallyconducting joint(s), elements with multiple curves, symmetricallyarranged segments of elements, non-symmetrically arranged segments ofelements, elements comprising outer coatings or layers of non-conductingmaterials, etc.

The embodiments of the present invention may be designed whereinindividual elements e.g. radiating element 112 have minimal or no sharpcorners to avoid undesirable regions of concentrated microwave field.

Antenna 104 may be designed to have a shape that substantiallyapproximates the shape of a target tissue to be ablated or the shape ofa lesion to be created. In one embodiment, antenna 104 has a roughlytriangular shape that is especially suited for endometrial ablation. Inanother embodiment, antenna 104 has a roughly linear shape such as thatshown in FIG. 1C that is especially suited for the ablation of a linearregion of tissue e.g. for the creation of a linear lesion in the leftatrium.

In FIG. 1C, the surface of radiating element 112 is enclosed within oneor more layers of dielectric materials. The thickness and type ofdielectric material along the length of radiating element 112 isengineered to optimize the microwave field shape. Thus one or moredielectric materials covering radiating element 112 may also be used asnon-conducting shaping elements to shape the microwave field. The one ormore dielectric materials covering radiating element 112 shape themicrowave field by changing the local dielectric environment in theregion adjacent to radiating element 112. In this embodiment, everyportion of radiating element 112 is covered with some dielectricmaterial such that no metallic surface of radiating element 112 isexposed to tissue. Thus, in this embodiment, radiating element 112 iselectrically insulated from tissue. Thus, in this embodiment, radiatingelement 112 is able to transmit a microwave field into tissue, butunable to conduct electricity to tissue. Thus, in this embodiment, thereis no electrical conduction and no conductive path between radiatingelement 112 and shaping element 114. Further, in this embodiment, thereis no electrical conduction and no conductive path between radiatingelement 112 and the surrounding tissue. In one embodiment, thedielectric on a proximal portion of radiating element 112 is acontinuation of the dielectric 110 of coaxial cable 102. The thicknessof a dielectric on radiating element 112 may vary along the length ofradiating element 112. Further, the crossection of a dielectric onradiating element 112 may not be radially symmetric.

In the embodiment of FIG. 1C, radiating element 112 is made of ahelically arranged length of a metallic conductor. The helix may besymmetric with a constant pitch and a constant diameter along the lengthof the helix. In one embodiment, the straightened length of theconductor used for constructing radiating element 112 is about threequarters of the effective wavelength at 915 MHz. In alternateembodiments, this length may be an odd multiple of one quarter of theeffective wavelength at one of: 433 MHz ISM band, 915 MHz ISM band, 2.45GHz ISM band and 5.8 GHz ISM band. Although in FIG. 1C, radiatingelement 112 has about 19 turns, embodiments of ablation devices 100 maybe constructed wherein radiating element 112 has about 1 to 30 turns.The pitch of a helical radiating element 112 may range between 0.3 mmand 20 mm. Radiating element 112 may be made from a metallic element oralloy selected from the group comprising Nitinol, stainless steel orcopper. Radiating element 112 may comprise a plating of a conductingmetal such as Ag or Au on the outer surface of radiating element 112.The metallic conductor used for constructing radiating element 112 mayhave a round, oval, rectangular or square crossection. In oneembodiment, the metallic conductor used for constructing radiatingelement 112 has a round crossection with a diameter of 0.5 mm+/−0.4 mm.In another embodiment, the metallic conductor used for constructingradiating element 112 has a rectangular crossection with crossectionaldimensions of 10 mm+/−9.5 mm by 0.5 mm+/−0.4 mm. In another embodimentof a radiating element with a rectangular crossection, the crossectionaldimensions are 1 mm+/−0.3 mm by 0.1 mm+/−0.05 mm. In an alternateembodiment, radiating element 112 is made of a length of a metallicconductor that is arranged in a substantially two dimensionalconfiguration. For example, the length of a metallic conductor may bearranged in a substantially wavy or zigzag or serpentine configuration.In the embodiment in FIG. 1C, radiating element 112 is arrangedsymmetrically around shaping element 114 and partially or fully enclosesshaping element 114. Shaping element 114 may be made of a linear orhelical length of a metallic conductor. The outer diameter of shapingelement 114 may be uniform or may be non-uniform along the length ofantenna 104. In the embodiment shown in FIG. 1C, shaping element 114 ismade of a substantially linear length of a metallic conductor. Shapingelement 114 may be made from a metallic element or alloy selected fromthe group comprising Nitinol, stainless steel or copper. Shaping element114 may comprise a plating of a conducting metal such as Ag or Au on theouter surface of shaping element 114. The metallic conductor used forconstructing shaping element 114 may have a round, oval, rectangular orsquare crossection. In one embodiment, the metallic conductor used forconstructing shaping element 114 has a round crossection with a diameterof 0.5 mm+/−0.3 mm. In another embodiment, the metallic conductor usedfor constructing shaping element 114 has a rectangular crossection withdimensions of 0.5 mm+/−0.3 mm by 0.5 mm+/−0.3 mm. Antenna 104 furthercomprises one or more antenna dielectrics 116 between radiating element112 and shaping element 114. In one embodiment, antenna dielectric 116is sufficiently flexible to create a flexible antenna 104. Theflexibility of antenna 104 allows antenna 104 to bend from asubstantially linear configuration to a substantially non-linearconfiguration and vice-versa during clinical use. The flexibility ofantenna 104 also allows antenna 104 to bend relative to the distal endof the transmission line during clinical use. This in turn allows a userto introduce antenna 104 to the target location through tortuous ornon-linear introduction paths such as blood vessels. In one embodiment,antenna dielectric 116 is sufficiently stiff to create a sufficientlystiff antenna 104. The stiffness of antenna 104 prevents antenna 104from bending during clinical use. This in turn enables the user to useantenna 104 to puncture or penetrate through tissue such as tumor tissueas shown in FIG. 7A. Examples of dielectrics that can be used betweenradiating element 112 and shaping element 114 include, but are notlimited to EPTFE, PTFE, FEP and other floropolymers, Silicone, Air,PEEK, polyimides, natural or artificial rubbers and combinationsthereof. Additionally the entire antenna 104 may be covered orencapsulated in a dielectric. Examples of dielectrics that can be usedto cover or encapsulate antenna 104 include, but are not limited toEPTFE, PTFE, FEP and other floropolymers, Silicone, PEEK, polyimides,natural or artificial rubbers and combinations thereof. Antennadielectric 116 may comprise one or more layers of such dielectrics. Thedielectric used to cover or encapsulate antenna 104 may be porous ornon-porous. In FIG. 1C, the length of antenna 104 is between 10 mm and80 mm. In FIG. 1C, the width of antenna 104 is between 1 mm and 40 mm.In one particular embodiment, antenna 104 has a length of 45 mm+/−7 mmand a width of 2 mm+/−0.5 mm. Radiating element 112 is electricallyconnected to inner conductor 108 of coaxial cable 102. This may be donefor example, by soldering or resistance welding radiating element 112 toinner conductor 108. Shaping element 114 is electrically connected toouter conductor 106 of coaxial cable 102. This may be done for example,by soldering or resistance welding shaping element 114 to outerconductor 106. Antenna 104 may be floppy, flexible or substantiallyrigid. Antenna 104 may be malleable or have shape memory or elastic orsuper-elastic properties. The distal end of antenna 104 may beatraumatic. Antenna 104 may be designed such that the length of antenna104 is adjustable. For example, length of antenna 104 may be increasedor reduced to increase or reduce the length of an ablation zone. In thisembodiment, shaping element 114 may have a helical or substantially wavyor zigzag or serpentine configuration. The length of antenna 104 may beincreased or reduced intra-operatively or pre-operatively. In oneembodiment, one or both of radiating element 112 and shaping element 114are a part of a flexible circuit and are manufactured using commonlyknown techniques for manufacturing flexible circuits.

In FIG. 1C, the shape of radiating element 112 is different from theshape of shaping element 114. Further in the embodiment in FIG. 1C,radiating element 112 is non-linear. Further in the embodiment in FIG.1C, shaping element 114 is substantially linear. However radiatingelement 112 and shaping element 114 are generally oriented such thattheir axes are parallel to each other. Alternate embodiments of antenna104 may be designed wherein radiating element 112 is substantiallylinear. Alternate embodiments of antenna 104 may be designed whereinshaping element 114 is substantially non-linear. Alternate embodimentsof antenna 104 may be designed wherein radiating element 112 and shapingelement 114 are generally oriented such that their axes are notparallel.

Although in the embodiment in FIG. 1C shaping element 114 is connectedto the distal end of coaxial cable 102, other embodiments of antenna 104may be designed wherein shaping element 114 is connected to coaxialcable 102 at a region other than the distal end of coaxial cable 102.For example, in one alternate embodiment, shaping element 114 ismetallic and is electrically connected to a region of outer conductor106 of coaxial cable 102 proximal to the distal end of the coaxial cable102.

In FIG. 1C, since radiating element 112 is in electrical contact withinner conductor 108, there is a first electrically conductive pathextending from inner conductor 108 till the distal end of radiatingelement 112. In the embodiments wherein shaping element 114 is made of aconductive material and is electrically connected to outer conductor 106of coaxial cable 102, there is a second electrically conductive pathextending from outer conductor 106 till the distal end of shapingelement 114. In such embodiments, even though there are two conductivepaths that extend from first zone Z1 to the second zone Z2, the designs,materials and the microwave properties of the two conductive paths maybe significantly different in first zone Z1 and second zone Z2 asdescribed before. In first zone Z1, outer conductor 106 of coaxial cable102 is located symmetrically around inner conductor 108 and at aconstant distance from inner conductor 108. However, in second zone Z2,radiating element 112 is located symmetrically around shaping element114 and at a constant distance from shaping element 114. In first zoneZ1, outer conductor 106 of coaxial cable 102 always acts as a shield forthe microwave field in first zone Z1 whereas in second zone Z2, shapingelement 114 may or may not act as a shield for the microwave field insecond zone Z2.

FIG. 1D shows a section through an embodiment of coaxial cable 102usable for ablation device 100 of FIG. 1C and for other ablation devices100 disclosed herein. In one embodiment, coaxial cable 102 used hereinis flexible and comprises an inner conductor 108 made of Nitinol with aNi content of 56%+/−5%. The outer diameter of inner conductor 108 is0.0172″+/−0.004″. Inner conductor 108 has a cladding or plating 120 of ahighly conductive metal such as Ag or Au. In one embodiment, innerconductor 108 comprises a silver cladding 120 of thickness0.000250″+/−0.000050″. Cladding 120 in turn is surrounded by dielectricmaterial 110. In one embodiment, dielectric material 110 is made ofexpanded PTFE with an outer diameter of 0.046″+/−0.005″. The dielectricmaterial 110 in turn is surrounded by the outer conductor 106. Outerconductor 106 acts as a shielding element to the microwave signalstransmitted by inner conductor 108. Further, outer conductor 106 shieldsthe microwave signals transmitted by inner conductor 108 from externalnoise. In one embodiment, outer conductor 106 comprises multiple strandsof Ag plated Cu. The multiple strands of outer conductor 106 arearranged such that the outer diameter of outer conductor 106 is0.057″+/−0.005″. Outer conductor 106 in turn is covered by an outerjacket 118. In one embodiment, outer jacket 118 is made of PTFE with anouter diameter of 0.065″+/−0.005″. Thus, the outer diameter of coaxialcable 102 is less than about 2 mm. The low profile of flexible coaxialcable 102 has tremendous clinical advantages since it can be insertedthrough narrow and/or tortuous anatomical paths or introducing devicelumens. In one embodiment, a shaft comprising coaxial cable 102 isstiffened or strengthened by adding one or more stiffening orstrengthening elements such as enclosing stiffening devices jackets,braids, or stiffening layers over coaxial cable 102. In one embodiment,antenna 104 is stiffened or strengthened by adding one or morestiffening or strengthening elements such as jackets, braids or layerswithin or over antenna 104.

FIG. 1E shows a longitudinal section of the embodiment of ablationdevice 100 of FIG. 1C through the distal end of coaxial cable 102. InFIG. 1E, the identity of coaxial cable 102 ends at the distal end ofouter conductor 106. Transition line 105 in FIG. 1E is located at thedistal end of outer conductor 106 and is substantially perpendicular tothe axis of coaxial cable 102 at the distal end of outer conductor 106.Outer jacket 118 of coaxial cable 102 terminates a small distanceproximal to the distal end of outer conductor 106. A conductive elementattached to the distal end of inner conductor 108 forms radiatingelement 112. In one embodiment, the proximal end of radiating element112 is electrically connected to the distal end of inner conductor 108.In one embodiment, the proximal end of radiating element 112 is solderedto inner conductor 108. In another embodiment, the proximal end ofradiating element 112 is laser welded to inner conductor 108. Theproximal end of radiating element 112 may be electrically connected toinner conductor 108 in various configurations including, but not limitedto lap joint and butt joint. The proximal end of shaping element 114 iselectrically connected to a region of outer conductor 106. In oneembodiment, the proximal end of shaping element 114 is electricallyconnected to the distal end of outer conductor 106. In one embodiment,the proximal end of shaping element 114 is soldered to outer conductor106. In another embodiment, the proximal end of shaping element 114 islaser welded to outer conductor 106. The proximal end of shaping element114 may be electrically connected to outer conductor 106 in variousconfigurations including, but not limited to lap joint and butt joint.

FIGS. 2A and 2B show two side views of a simulated SAR profile generatedby the device embodiment of FIG. 1C. FIG. 2C shows a top view of asimulated SAR profile generated by the device embodiment of FIG. 1C.FIG. 2C demonstrates that the SAR profile generated by the deviceembodiment of FIG. 1C is substantially radially symmetric andcircumferentially envelops entire antenna 104. FIGS. 2A and 2Bdemonstrate that the microwave field generated by antenna 104 of FIG. 1Cis substantially restricted to second zone Z2. There is an insignificantamount of the microwave field in first zone Z1 containing coaxial cable102. Thus, there is negligible backward coupling between the microwavefield and the distal portion of coaxial cable 102. This in turn reducesthe risk of ablating tissue proximal to the distal end of coaxial cable102. Further, the microwave field is substantially uniform along thelength of antenna 104 as compared to a comparable monopole antenna. Thusthe lesion formed by the microwave field in FIGS. 2A and 2B will beuniform and substantially localized to the extent of antenna 104. Also,FIGS. 2A and 2B show that the microwave field volumetrically envelopsentire antenna 104. Thus, embodiments of linear antenna 104 designed tooperate at 915 MHz and other microwave frequencies may be designed thatcan create uniform, symmetrical, continuous, linear lesions with alesion length greater than 35 mm.

In alternate embodiments, the SAR profile may be designed to besubstantially non-uniform along the length of a linear antenna 104. Forexample, an antenna 104 may be designed to have a SAR profile that iswider and/or stronger at the center of antenna 104 and is less strong atthe ends of antenna 104. In order to achieve this, one or more designparameters of antenna 104 in FIG. 1C may be modified. Examples of suchmodifications include, but are not limited to: adding of one or moreadditional conductive shaping elements 114; varying the width and/or thecrossection shape of shaping element 114 and/or radiating element 112along the length of antenna 104; varying the pitch of helical radiatingelement 112 and/or helical shaping element 114 along the length ofantenna 104; varying the thickness, type and other design parameters ofone or more antenna dielectrics 116, etc.

FIG. 2D shows the simulated return loss of an ablation device with anantenna of FIG. 1C. The simulated return loss shows good matching (about−13.35 dB) at 915 MHz.

Antenna 104 in FIG. 1C has several advantages over a comparable monopoleantenna. FIGS. 2E and 2F show a side view and the top view respectivelyof a simulated SAR profile generated by a monopole antenna. FIG. 2Eshows the presence of a region of concentrated microwave field or a “hotspot” near the distal end of the transmission line (e.g. a coaxialcable) or at the proximal end of the monopole antenna. Thus themicrowave field in FIG. 2E is non-uniform as compared to the field inFIG. 2B. About half of the microwave field in FIG. 2F is present infirst zone Z1. Thus, there is a significant amount of microwave fieldpresent in first zone Z1. Thus, there is a high risk of ablating tissueproximal to the distal end of coaxial cable 102. The presence of asignificant amount of microwave field in first zone Z1 is due toundesirable coupling between the microwave field and the outer conductorof the coaxial cable or other transmission line. This undesirablecoupling can also cause backward heating of coaxial cable 102 that maylead to collateral damage of healthy tissue.

In several of the embodiments herein, shaping element 114 plays acritical role in shaping the microwave field generated by antenna 104.FIG. 2G shows a side view of a simulated SAR profile generated by thedevice embodiment of FIG. 1C without shaping element 114. The microwavefield shown in FIG. 2G is an unshaped field since it is not shaped byshaping element 114. It is seen that antenna 104 in FIG. 2G behavessimilar to a monopole antenna of FIG. 2E. FIG. 2G shows the presence ofa region of concentrated microwave field or a “hot spot” near the distalend of the coaxial cable 102 or at the proximal end of the antenna 104.Thus the unshaped microwave field in FIG. 2G is non-uniform as comparedto the shaped microwave field shaped by shaping element 114 in FIG. 2B.About half of the unshaped microwave field in FIG. 2G is present infirst zone Z1. Thus, there is a significant amount of microwave fieldpresent in first zone Z1. Thus, there is a high risk of ablating tissueproximal to the distal end of coaxial cable 102. The presence of asignificant amount of microwave field in first zone Z1 is due toundesirable coupling between the microwave field and the outer conductorof the coaxial cable 102 or other transmission line. This undesirablecoupling can also cause backward heating of coaxial cable 102 that maylead to collateral damage of healthy tissue. FIG. 2H shows the simulatedreturn loss (solid line) of an ablation device with an antenna of FIG.1C without shaping element 114. The simulated return loss shows amatching (about −9.41 dB) at 915 MHz that is much lower in magnitudethan the good matching (about −13.35 dB) at 915 MHz obtained with theantenna of FIG. 1C (dashed line in FIG. 2H). Thus, the design of shapingelement 114 in antenna 104 of FIG. 1C improves the matching.

Shaping element 114 may be used to provide an additional resonance pointin the frequency spectrum. This in turn may be used to increase thefrequency range (bandwidth) over which antenna 104 delivers anacceptable performance. For example, the design of shaping element 114in FIG. 1C improves the frequency range over which important performanceparameters are acceptable. In FIG. 2H if the solid and dashed lines arecompared, at a cutoff of −10 dB, the acceptable frequency range in theembodiment containing shaping element 114 is about 0.23 GHz (spanningfrom approximately 0.87 GHz to approximately 1.10 GHz). The acceptablefrequency range in the comparable embodiment of FIG. 2G without shapingelement 114 is only about 0.19 GHz (spanning from approximately 0.93 GHzto approximately 1.12 GHz). Thus in the first case, a larger frequencyrange (bandwidth) is available over which antenna 104 delivers anacceptable performance. This in turn allows for a design of antenna 104wherein minor distortions of antenna 104 during typical clinical use ordue to minor manufacturing variations do not significantly affect theperformance of antenna 104.

FIG. 2I shows a photograph of a fully functional, linear antenna similarto the design in FIG. 1C. In FIG. 2I, the multiple turns of radiatingelement 112 surround shaping element 114 (not visible). Entire antenna104 is covered with a layer of a transparent dielectric material. Thelinear length of antenna 104 from the distal end of coaxial cable 102till the distal end of radiating element 112 is about 4.5 cm. Alternateembodiments of antenna 104 may be designed with a linear length rangingfrom 2.5-5.5 cm. The outer diameter of antenna 104 in FIG. 2I is about 2mm. Alternate embodiments of antenna 104 may be designed with an outerdiameter ranging from 1.5-4 mm.

FIG. 2J shows an experimental setup for demonstrating the utility ofantenna 104 of FIG. 2I for intra-cardiac ablation and otherapplications. In FIG. 2J, a slice of porcine muscle tissue is kept in awater bath maintained at 37 C. Further, water is pumped in the waterbath from a nozzle 125 and is continuously circulated through the waterbath using a pump (not shown). This is to simulate the effect of bloodflow within the heart chambers. FIG. 2J shows an unablated slice ofporcine muscle tissue.

FIGS. 2J-2N show the method steps of a method of creating twooverlapping lesions in a tissue. In FIGS. 2J-2N, the method isdemonstrated in the setup of FIG. 2J. In FIG. 2J, a linear antenna 104of FIG. 2I is placed in contact with the porcine tissue as shown.Thereafter, microwave power at 0.915 GHz is delivered to ablation device100 at 80 W for 60 s. FIG. 2L shows a first ablation created aroundantenna 104. In FIG. 2M, antenna 104 is moved to a new location.Thereafter, microwave power is delivered to ablation device 100 at 80 Wfor 60 s to create a second lesion as shown in FIG. 2N. In FIG. 2N,antenna 104 is being moved away after creating the second lesion.Various patterns of multiple lesions may thus be created byrepositioning any of the antennas 104 disclosed herein. Any of theantennas 104 disclosed herein may be repositioned by one or more of:rotating around an axis, moving proximally or distally, moving sideways,revolving around an axis, increasing or reducing in size, engaging asteering or deflecting mechanism on ablation device 100 and engaging asteering or deflecting mechanism on an accessory device. Further, any ofthe antennas 104 disclosed herein may be designed and used such thatduring clinical use the forces exerted by a flexible antenna 104 onsurrounding tissues do not distort the surrounding tissue. In oneembodiment, two lesions are created that do not intersect each other. Inanother embodiment, two elongate lesions are created that are joinedlengthwise. In another embodiment, two elongate lesions are created thatare joined breadthwise. In another embodiment, two elongate lesions arecreated that intersect each other to form an approximately X-shapedresulting lesion.

FIG. 2O shows a surface view of the two resulting overlapping lesionsobtained from the method in FIGS. 2J-2N. In FIG. 2O, it is seen that thevisual zone of ablation extends about 6-10 mm in breadth and about 9 cmin total length. By changing one or more of: ablation time, ablationpower, antenna 104 design, antenna 104 position, the length and/or thebreadth of the lesion may be varied.

FIG. 2P shows a view of the section through the plane 2P-2P in FIG. 2Oshowing two deep, overlapping lesions. In FIG. 2P, the length of thecombined lesion is about 9 cm and the visual depth of the lesion variesfrom 1-1.5 cm. Thus, long, deep lesions may be created by antenna 104.The lesions may be created such that they span the entire thickness ofthe tissue such as a heart wall. Thus antenna 104 can be used to createtrans-mural lesions. Further, there is a complete absence of charring inthe lesion. Also, long, deep lesions were created even in the presenceof flowing fluid. Thus antenna 104 may be used to create lesions inanatomical regions that contain flowing blood such as the vasculature(veins, arteries, etc.) and the heart chambers.

FIGS. 2Q and 2R show a uniform lesion created by the antenna in FIG. 2Iin a bent or curved configuration. In FIG. 2R, the antenna 1904 has beenmoved away to show the underlying lesion. FIGS. 2Q and 2R show that thelesion is bent or curved and corresponds to the bent or curved profileof antenna 104. Further, there is no burning or charring of the surfaceof the tissue. Thus antenna 104 embodiments such as the embodiment inFIG. 1C are capable of creating uniform lesions even in a bent or curvedconfiguration. This is very important in applications such aselectrophysiological ablation of cardiac tissue for treating arrhythmiaswhere the ability to create long, curved or bent lesions enables theuser to complete the procedure faster and with improved outcomes.

Any of the antennas 104 herein such as linear antenna 104 of FIG. 1C maybe shaped or otherwise modified for a variety of specific applications.FIGS. 3A-3D show embodiments of antenna 104 wherein antenna 104 haslinear, curved, closed loop and helical shapes respectively. The shapeembodiments shown in FIGS. 3A-3D may have a fixed shaped or may beuser-shapeable. For example, antenna 104 may be provided with a pullwire or a similar shape distorting element to reversibly change theshape of antenna 104 from a linear shape as shown in FIG. 3A to a morecurved or bent shape as shown in FIG. 3B and vice versa. In anotherexample, a distal region of antenna 104 may be provided with a pull wireor a similar shape distorting element to reversibly change the shape ofantenna 104 from a linear shape as shown in FIG. 3A to a more loopedshape as shown in FIG. 3C and vice versa. Examples of mechanisms thatmay be used to change the shape of antenna 104 include, but are notlimited to internal or external pull wires, balloons, inflatablestructures and straight or bent slidable stylets. Any of the antennas104 disclosed herein may be used to create ablations that substantiallycorrespond to the shape of antenna 104. For example, antenna 104 in FIG.3A may be used to create a substantially linear lesion, antenna 104 inFIG. 3B may be used to create a substantially curved or bent lesion,antenna 104 in FIG. 3D may be used to create a helical lesion, etc. Anyof the antennas 104 disclosed herein may be used to create ablationsthat do not substantially correspond to the shape of antenna 104. Forexample, antenna 3C may be used to create a round lesion, a point lesionor a linear lesion as better illustrated in FIGS. 3I-3L. Any of theantennas 104 disclosed herein may be used to penetrate through a bodytissue to ablate a target. To facilitate the penetration though tissue,a distal end of any of antenna 104 disclosed herein may be modified(e.g. by having a sharp tip) to facilitate a penetration of tissue. Forexample, antenna 104 of FIG. 3A may be designed to be sufficiently stiffand have a sharp distal tip to penetrate skin to ablate abdominal andother internal organs. Alternately, antenna 104 of FIG. 3A may bedesigned to be sufficiently flexible to enable the introduction ofantenna 104 through natural openings and passages of the body or througha catheter. In another example, antenna 104 of FIG. 3D may be designedto be sufficiently stiff and have a sharp distal tip to penetrate atissue surface and be insertable in a corkscrew-like manner to accessunderlying tissue. In another embodiment, antenna 104 of FIG. 3D isdesigned to be sufficiently flexible and collapsible to enable theintroduction of antenna 104 through natural openings and passages of thebody or through a catheter. The elastic or super-elastic or shape memorynature of antenna 104 may then enable antenna 104 to regain a helicalshape after reaching a target tissue such as a lumen of a body passageor cavity e.g. a blood vessel.

Any of the antenna 104 disclosed herein may be repositioned once ormultiple times during a procedure to access multiple regions of thebody. This repositioning may be done by moving the whole or a part ofablation device 100. FIG. 3E shows an embodiment of an ablation devicecomprising a steerable or deflectable antenna. In FIG. 3E, ablationdevice 100 comprises an antenna 104 that is controllably steerable ordeflectable. Thus, antenna 104 is able to access various target regionswithout moving entire ablation device 100. In one embodiment, ablationdevice 100 of FIG. 3E is inserted into a cavity or a lumen. Examples ofsuch cavities or lumens include, but are not limited to: natural orartificially created cavities or lumens in portions of the male urinarytract, gall bladder, uterus and other portions of the femalereproductive tract, regions of the vasculature, intestine and otherportions of the lower alimentary tract, stomach and other portions ofthe upper alimentary tract, liver and other digestive organs, lungs,skin, mucus membranes, kidneys, reproductive organs, or other organs orsoft tissues of the body. Antenna 104 is positioned to access a firstregion of tissue and is used to ablate the first region of tissue.Thereafter, antenna 104 is deflected to access a second region of tissueand is used to ablate the second region of tissue. Thus, multipleregions of tissue may be ablated by antenna 104. Examples of mechanismsthat may be used to steer or deflect antenna 104 include, but are notlimited to internal or external pull wires, balloons, inflatablestructures and straight or bent slidable stylets. Even though a linearantenna is shown in FIGS. 3E and 3F, any of the antennas 104 disclosedherein may be used to construct ablation device 100 in FIGS. 3E and 3F.In one embodiment, an entire target tissue area is ablated withoutrepositioning the entire ablation device 100 while repositioning antenna104 once or more. For example, an entire uterine endometrium may beablated by an ablation device 100 that is inserted through the cervixinto the uterine cavity after positioning an antenna 104 at at least 2positions in the uterine cavity.

FIG. 3F shows an embodiment of an ablation device 100 that isrepositioned to ablate multiple target regions. In FIG. 3F, a majorityor all or ablation device 100 is repositioned to access multiple targetregions. In one such embodiment, antenna 104 is placed on a firstposition on the surface of the liver and is used to ablate a firstregion of the liver. Thereafter, ablation device 100 is moved toposition antenna 104 at a second position on the surface of the liverand antenna 104 is used to ablate a second region of the liver. Ablationdevice 100 may be moved sideways, forwards or backwards or in any othersuitable motion. In a method embodiment, ablation device 100 isreinserted into a tissue after a first ablation to abate another regionof tissue. For example, antenna 104 may be inserted inside the liver ata first position and is used to ablate a first region in the interior ofthe liver. Thereafter, antenna 104 is removed from the liver.Thereafter, antenna 104 is reinserted inside the liver at a secondposition and is used to ablate a second region in the interior of theliver. In another example, ablation device 100 is inserted in a heartcavity and antenna 104 is used to ablate a first region of the heartcavity to create a first lesion. Thereafter, antenna 104 is moved to asecond location of the heart cavity and is used to ablate the secondregion of the heart cavity to create a second lesion. The first andsecond lesions may be overlapping or non-overlapping. In case ofoverlapping lesions, the first and second lesions may overlap in asubstantially end-to-end or side-to-side overlap.

FIGS. 3G-3H show two configurations of a microwave device having anantenna that can be reversibly converted between a straightconfiguration and a bent configuration. In FIG. 3G, antenna 104 issubstantially linear. A distal region of antenna 104 is connected to apull wire or a tether. Tether may be located external to ablation device100 and pass through an opening located on ablation device shaft. Theopening may for example by an opening of an end-to-end lumen, an openingof a rapid-exchange lumen, an opening of a collapsible lumen, a loopetc. The proximal region of tether can be manipulated by a user. In FIG.3H, a bending force is exerted on antenna 104. This bending force inturn causes antenna 104 to bend and assume a substantially non-linearshape such as in FIG. 3H. In FIG. 3H, antenna 104 has a substantiallycircular, closed loop shape. Examples of other non-linear shapesinclude, but are not limited to other closed loop shapes, open loopedshapes, shapes enclosing one or more bends or curves, etc. Upon therelease of the bending force, antenna 104 returns back to thesubstantially linear shape of FIG. 3G by elastic or super-elasticproperty of antenna 104. In an alternate embodiment, antenna 104 has anon-linear configuration that is reversibly converted to a substantiallylinear configuration on the application of a bending force.

The ablation device in FIGS. 3G and 3H may be used to create a varietyof lesions such as small, localized “point” lesions, linear lesions,area lesions and volumetric lesions. For example, FIG. 3I shows anembodiment of a method used to create a small, localized “point” lesionon a tissue using the ablation device of FIGS. 3G and 3H. In FIG. 3I,antenna 104 is in a non-linear configuration. A portion of the antenna104 is in contact with tissue. The contact between antenna 104 and thetissue is made with a force sufficient to enable antenna 104 to contactthe tissue but not sufficient to distort or flatten antenna 104.Thereafter, energy is delivered by antenna 104 to the tissue to createthe “point” lesion. FIG. 3J shows an embodiment of a method used tocreate a linear lesion on a tissue using the ablation device of FIGS. 3Gand 3H. In FIG. 3J, antenna 104 is in a non-linear configuration. Aportion of the antenna 104 is in contact with tissue. The contactbetween antenna 104 and the tissue is made with a force sufficient todistort or flatten antenna 104 such that the contact surface betweenantenna 104 and the tissue is substantially linear. Thereafter, energyis delivered by antenna 104 to the tissue to create the substantiallylinear lesion. FIG. 3K shows an embodiment of a method used to create anannular lesion on a tissue using the ablation device of FIGS. 3G and 3H.In FIG. 3K, antenna 104 is in a non-linear configuration. A portion ofthe antenna 104 is in contact with tissue. The contact between antenna104 and the tissue is made such that antenna 104 is substantially in theplane of the tissue surface. Thereafter, energy is delivered by antenna104 to the tissue to create the substantially annular lesion. Variousparameters such as the ablation time, ablation power, etc. may bechanged or manipulated in any of the methods described herein to achievethe desired clinical outcome. The microwave energy may be delivered in acontinuous mode or in a discontinuous mode. In the embodiment in FIG.3K, microwave energy is delivered such that the region of tissueimmediately adjacent to antenna 104 is ablated. This creates an annularlesion as shown in FIG. 3K. FIG. 3L shows an embodiment of a method usedto create a round lesion on a tissue using the ablation device of FIGS.3G and 3H. In FIG. 3L, antenna 104 is in a non-linear configuration. Aportion of the antenna 104 is in contact with tissue. The contactbetween antenna 104 and the tissue is made such that antenna 104 issubstantially in the plane of the tissue surface. Thereafter, energy isdelivered by antenna 104 to the tissue to create the substantially roundlesion. In the embodiment in FIG. 3L, microwave energy is delivered fora longer time and/or with higher power than in the method in FIG. 3Ksuch that a round shaped region of tissue adjacent to antenna 104 isablated. This round lesion may be restricted to the surface of thetissue. Alternately, with a higher ablation power and/or longer ablationtime, the lesion may extend sufficiently deep into the tissue to createa volumetric lesion.

The shape of antenna 104 may be modified during a procedure to targettwo different regions of target tissue. For example, antenna 104 of FIG.1C may be inserted inside tissue (e.g. liver, brain, etc.) and used toablate tissue deep inside the organ. In order to achieve this, antenna104 (e.g. antenna 104 of FIG. 1C) may be inserted while enclosed insidea sufficiently stiff outer sheath made of a dielectric material. In thesame procedure, antenna 104 may be bent or curved as shown in FIGS. 3Kand 3L and thereafter used to ablate a surface of organ. This eliminatesthe need for two separate devices—one for ablating deeper tissue and onefor ablating surface tissue. This in turn will reduce the procedurecomplexity and costs.

FIGS. 4A and 4B show two method embodiments of ablating tissue wherein aradiating element and a shaping element of an antenna are placed onopposite sides of the tissue. In FIG. 4A, ablation device 100 isintroduced in a lumen 130 or a body cavity. Examples of such lumens 130or body cavities include but are not limited to: natural or artificiallycreated cavities or lumens in portions of the male urinary tract, gallbladder, uterus and other portions of the female reproductive tract,regions of the vasculature, intestine and other portions of the loweralimentary tract, stomach and other portions of the upper alimentarytract, liver and other digestive organs, lungs, skin, mucus membranes,kidneys, reproductive organs, or other organs or soft tissues of thebody. Antenna 104 is positioned near the target tissue such thatradiating element 112 and shaping element 114 are placed on oppositesides of the target tissue. In FIG. 4A, radiating element 112 is locatedin the lumen 130 while shaping element 114 is located outside lumen 130.Antenna 104 is used to ablate a portion of the wall of lumen 130.Shaping element 114 may be located inside the tissue of the wall oflumen 130 or may be passed through a natural or artificially createdopening to a location outside lumen 130 as shown in FIG. 4A. Shapingelement 114 shapes the microwave field emitted by radiating element 112such that the microwave field is concentrated in the region betweenradiating element 112 and shaping element 114. This concentratedmicrowave field in the region between radiating element 112 and shapingelement 114 is used to ablate tissue. In FIG. 4B, shaping element 114 islocated in the lumen 130 while radiating element 112 is located outsidelumen 130.

FIGS. 4C and 4D show two method embodiments of ablating tissue locatedbetween an antenna and a microwave shield or reflector. FIG. 4C shows amethod embodiment of ablating tissue in a wall of the uterus locatedbetween an antenna and a microwave shield or reflector. In FIG. 4C, anantenna 104 is introduced inside the uterine cavity. Antenna 104generates a microwave field that is used to ablate tissue adjacent toantenna 104. In FIG. 4C, antenna 104 is navigated in the uterine cavityand is placed adjacent to the target tissue to be ablated. Examples ofsuch target tissues include, but are not limited to: fibroids, cancerouslesions, adenomyosis, polyps and portions of the endometrium. Further,in FIG. 4C, a microwave reflector or shield 132 is placed on theexternal surface of the uterus i.e. on the surface of the uterineserosa. Microwave reflector or shield 132 is used to shield or reflectany microwave energy that reaches the external surface of the uterus.Microwave reflector or shield 132 may be made of conductive ordielectric materials or combinations thereof. This increases the safetyof the procedure by reducing the risk of collateral damage of tissue.Microwave reflector or shield 132 may be introduced through alaparoscopic incision, trans-vaginally, through a laparotomy, or throughother methods known in the art to introduce devices on the surface ofthe uterus. In an alternate embodiment, the positions of antenna 104 andmicrowave reflector or shield 132 are swapped. In this embodiment, themicrowave reflector or shield 132 is not a part of antenna 104.

FIG. 4D shows a method embodiment of ablating tissue in a wall of theuterus similar to the method in FIG. 4C. However, in FIG. 4D, microwavereflector or shield 132 is introduced in the desired position through atrans-vaginal approach. Microwave reflector or shield 132 may or may notbe electrically connected to one or more portions of coaxial cable 102such as outer conductor 106. In this embodiment, the microwave reflectoror shield 132 may or may not be a part of antenna 104. Similar to themethod in FIG. 4C, the positions of antenna 104 and microwave reflectoror shield 132 may be swapped. Methods similar to those illustrated inFIGS. 4C and 4D may be used to treat other anatomical regions such asanatomical cavities or lumens or tissue volumes. In one such embodiment,an antenna 104 is placed in an endocardial location and a microwavereflector or shield 132 is placed in a pericardial location or viceversa. Microwave reflector or shield 132 may be made of conductive ordielectric materials or combinations thereof. In one antenna 104embodiment, a shaping element 114 may act as a microwave reflector orshield 132.

FIG. 5A shows an embodiment of a portion of an antenna built on aprinted circuit board. In FIG. 5A, a portion of antenna 104 is printedon a rigid or flexible, generally planar printed circuit board. In anyof the embodiments herein, the whole or portions of antenna 104 may beprinted on one or more rigid or flexible, planar or non-planar printedcircuit boards.

The devices and methods disclosed herein and modifications thereof maybe used during minimally invasive or invasive treatment of tissue. Forexample, FIG. 6A shows an embodiment of an ablation device with a threedimensional antenna comprising a radiating element and multiple shapingelements adapted to ablate a volume of tissue. In FIG. 6A, ablationdevice 100 comprises an antenna 104 comprising a substantially linearradiating element 112. Antenna 104 further comprises a plurality ofshaping elements 114. In FIG. 6A, the four shaping elements 114 areidentical and are arranged symmetrically around radiating element 112.Embodiments of antenna 104 may be designed with 1-10 shaping elements114. Shaping elements 114 may be symmetrically or non-symmetricallyarranged around radiating element 112. Shaping elements 114 may or maynot be identical. In FIG. 6A, each shaping element 114 is elongate andcomprises a bend or an angled region. In FIG. 6A, each shaping elementis electrically connected to the outer conductor of coaxial cable 102 orother transmission line. The distal end of radiating element 112 and/orshaping elements 114 may comprise a sharp or penetrating tip. In oneembodiment, shaping elements 114 are a retractable claw structure thatextends from ablation device 100. In one embodiment, the design ofradiating element 112 is similar to a 14 mm long monopole antenna. InFIG. 6A, shaping elements 114 shape and enhance the electromagneticfield in the volume between radiating element 112 and shaping elements114. This creates a large, volumetric lesion between radiating element112 and shaping elements 114. The volumetric lesion will besubstantially confined to the extent of shaping elements 114 as seenfrom FIGS. 6B and 6C. Further, shaping elements 114 reduce the leakagecurrent that will otherwise be induced on the outer wall of the outerconductor of coaxial cable 102 or other transmission line.

When microwave energy is delivered through a transmission line toantenna 104 in FIG. 6A, a first microwave field is emitted by radiatingelement 112. The first microwave field interacts with shaping elements114. This interaction induces a leakage current on shaping elements 114.The leakage current in turn creates a second microwave field. The firstmicrowave field and the second microwave field together combine toproduce a unique shaped microwave field of antenna 104 that isclinically more useful that the unshaped microwave field generated by anantenna 104 comprising only radiating element 112. Thus the originalmicrowave field is redistributed by the design of shaping elements 114.Shaping elements 114 alone are not capable of functioning as an antenna;rather shaping elements 114 shape or redistribute the electromagnetic ormicrowave field emitted by radiating element 112 to produce a shapedmicrowave field that is clinically more useful. Further, the combinationof radiating element 112 and shaping elements 114 improves the powerdeposition of antenna 104.

The microwave effect of shaping elements 114 can be seen by comparingFIG. 2E to FIG. 6B. In absence of shaping elements 114, antenna 104 inFIG. 6A acts as a monopole antenna similar to that shown in FIG. 2B.Thus FIG. 2B shows a first unshaped field that is not shaped by shapingelements 114. When the antenna 104 comprises shaping elements 114 asshown in FIG. 6A, the antenna generates a shaped microwave field asshown in FIG. 6B.

In an embodiment of a minimally invasive procedure, antenna 104 isinserted into the patient's body through small puncture wounds in theskin. Thereafter, antenna 104 is deployed such that the volume enclosedby the claw-like shaping elements 114 encloses the target tissue. Forexample, for cancer treatment, the target tissue is a tumor or a tissuewith cancer cells. The degree of deployment of antenna 104 may beadjusted to suit different target tissue sizes (e.g. different tumorsizes). In one such embodiment, one or more pull wires or tethers areattached to shaping elements 114 to control the position of shapingelements 114. In another embodiment, shaping elements 114 are pre-shapedand are made of a material with shape memory properties such as Nitinol.Shaping elements 114 are retracted inside a catheter or a tubularstructure in a collapsed configuration before inserting into the tissue.A low-profile catheter or a tubular structure is preferably used toreduce the trauma to healthy tissues during the insertion procedure.Once a portion of the catheter or tubular structure is inserted insidethe target tissue, shaping elements 114 and radiating element 112 aredeployed. Shaping elements 114 are deployed to their un-collapsed,preset shape by extending them from the catheter or tubular structure.Even though antenna 104 of FIG. 6A can be used for a variety ofprocedures, it is especially suited for ablating solid tumors such asthose found in cancer (e.g. liver and lung cancer) and benign tumors(e.g. uterine fibroids).

FIGS. 6B and 6C show a side view and a top view of a simulated SARprofile of an embodiment of the antenna of FIG. 6A. The SAR profile wassimulated at 2.45 GHz using the COMSOL Multiphysics package to simulatean ablation in the liver. FIGS. 6B and 6C illustrate that a volumetriclesion created by antenna 104 will be substantially confined to theextent of shaping elements 114. Also, FIGS. 6B and 6C show that themicrowave field volumetrically envelops entire antenna 104.

FIGS. 6D and 6E show a side view and a top view of a thermal simulationof an embodiment of the antenna of FIG. 6A. The outer most surface ofthe black zone is a 50° C. isosurface with a diameter or width of about28 mm and longitudinal length of about 22 mm at steady state. Thus,antenna 104 is capable for forming a lesion with a diameter or width ofabout 28 mm and longitudinal length of about 22 mm. The 50° C.isosurface encloses the 60° C. isosurface (boundary between the blackand dark grey zones) which in turn encloses the 70° C. isosurface(boundary between the dark grey and light grey zones) which in turnencloses the 80° C. isosurface (boundary between the light grey andwhite zones).

FIGS. 6F and 6G show a side view and a top view of a simulated SARprofile at 0.915 GHz of an embodiment of an antenna similar to theantenna of FIG. 6A. The SAR profile was simulated at 0.915 GHz using theAnsoft HFSS package to simulate an ablation in the liver. Radiatingelement 112 in FIGS. 6F and 6G is linear and has a length of about aquarter of the effective wavelength. FIGS. 6F and 6G illustrate that thevolumetric lesion will be substantially confined to the extent ofshaping elements 114.

The antenna 104 shown in FIGS. 6F and 6G comprises a substantiallylinear radiating element 112 with a plurality of shaping elements 114.The four shaping elements 114 shown in FIGS. 6F and 6G are identical andare arranged symmetrically around radiating element 112. Embodiments ofantenna 104 may be designed with 1-10 shaping elements 114 arrangedsymmetrically or non-symmetrically arranged around radiating element112. Shaping elements 114 may or may not be identical. In FIGS. 6F and6G, each shaping element is elongate and comprises two bends or angledregions. Similar to the embodiment in FIG. 6A, each shaping element iselectrically connected to the outer conductor of coaxial cable 102. Thedistal end of radiating element 112 and/or shaping elements 114 maycomprise a sharp or penetrating tip. In one embodiment, shaping elements114 are a retractable claw structure that extends from ablation device100. In FIGS. 6F and 6G, shaping elements 114 enhance theelectromagnetic field in the space between radiating element 112 andshaping elements 114. This creates a large, volumetric lesion betweenradiating element 112 and shaping elements 114. The volumetric lesion issubstantially confined to the extent of shaping elements 114 as shown inFIGS. 6F and 6G. Further, shaping elements 114 reduce the leakagecurrent that will otherwise be induced on the outer wall of the outerconductor of coaxial cable 102.

In FIGS. 6F and 6G, radiating element 112 comprises an elongateconductor that is about 34 mm long. The distal end of the elongateconductor is covered by a metallic tubular cap that is in conductivecontact with the elongate conductor. The outer diameter of theconductive cap is about 0.8 mm and the length of the conductive cap isabout 6 mm. The conductive cap is arranged such that the distancebetween the proximal end of the conductive cap and the distal end of thecoaxial cable is about 28 mm. Entire radiating element 112 is coveredwith a layer of dielectric material. Each shaping element 114 comprisesa proximal bend and a distal bend. The proximal bend is arranged at alongitudinal distance of about 15 mm measured along the length of theradiating element 112. The longitudinal distance between the proximalbend and the distal bend measured along the length of the radiatingelement 112 is about 15 mm. The longitudinal distance between the distalbend and the distal end of shaping element 114 measured along the lengthof the radiating element 112 is about 4 mm. Thus the total longitudinallength of each shaping element 114 measured along the length ofradiating element 112 is about 34 mm. The total diameter of thestructure formed by shaping elements 114 is about 30 mm. The use ofantenna 104 in FIGS. 6F and 6G is similar to antenna 104 of FIG. 6A.

FIG. 6H shows the simulated return loss of an ablation device with anantenna of FIGS. 6F and 6G. The simulated return loss shows goodmatching (about −11.4 dB) at 0.915 GHz.

FIG. 7A shows an embodiment of a substantially linear antenna used topenetrate a bodily tissue and ablate a tumor. In FIG. 7A, antenna 104 issimilar to antenna 104 of FIG. 1C with a helical radiating element 112and a substantially linear shaping element 114. However, antenna 104 inFIG. 7A has a sufficient mechanical strength to penetrate tissue.Further, antenna 104 in FIG. 7A comprises a distal penetrating tip 134.The length of ablation device 100 may range from 5 cm to 60 cm. Ablationdevice 100 may be introduced through a surgical incision such as alaparotomy or a thoracotomy. Ablation device 100 may also be introducedthrough a surgical instrument port such as a port for laparoscopic orthoracoscopic instruments. Ablation device 100 may be introducedpercutaneously by penetrating the skin using distal penetrating tip 134and advancing antenna 104 into target tissue. Such percutaneousintroduction may be used for example, to ablate liver or lung or uterinetumors with appropriate guidance such as radiological guidance or visualor endoscopic guidance. The low profile of antenna 104 enables antenna104 to be introduced multiple times at different regions in the targettissue sequentially without causing excessive damage to healthy tissue.Multiple ablation devices 100 may also be introduced simultaneously inthe target tissue to ablate a larger region of tissue.

FIGS. 8A-8D show the steps of a method of minimally invasive treatmentfor treating venous reflux disease or varicose veins. In this method, amicrowave device 100 is used to heat one or more regions of a targetvein. In one embodiment, one or more regions of a target vein are heatedto a temperature ranging between 80° C.-85° C. This temperature may beperformed as an outpatient procedure to cause therapeutic fibrotic veinocclusion by controlled heating of the vein. The fibrotic vein occlusionmay be caused by one or more of endothelial destruction, collagencontraction and vein wall thickening. In FIG. 8A, microwave device 100is introduced into the target vein lumen through a small skin incision.Microwave device 100 is positioned at a distal region within the lumenof the target vein. The introduction and/or the navigation of microwavedevice 100 in the body may be guided using a suitable guidance modality.Examples of such modalities include, but are not limited to: ultrasoundimaging (e.g. duplex ultrasound imaging), trans-illumination,fluoroscopic imaging and X-ray imaging. Once antenna 104 is positionedat the desired position, antenna 104 is used to deliver microwave energyto the target vein. Thereafter, in FIG. 8B, antenna 104 is positioned inthe target vein at a position proximal to the position of FIG. 8A. Onceantenna 104 is positioned at the desired position, antenna 104 is againused to deliver microwave energy to the target vein. The areas of thetarget vein that are treated in FIG. 8A and 8B may overlap. This processis continued as shown in FIGS. 8C and 8D until the target vein istreated. The delivered microwave energy heats the vein and causes thevein to shrink. In one embodiment, microwave device 100 is deliveredover a guidewire such as a 0.025″ guidewire or a 0.035″ guidewire or a0.014″ guidewire. Temperature sensing and/or impedance measurement atone or more locations on microwave device 100 and/or the target vein maybe used to control the procedure. Such temperature sensing and/orimpedance measurement may be used to adjust the power and/or time ofmicrowave energy delivery. Although a substantially linear antenna 104is depicted in FIGS. 8A-8D, any of the suitable antenna 104 embodimentsdisclosed herein may be used. For example, a helical antenna 104 in FIG.3D may be used for this procedure. In one such embodiment, antenna 104e.g. helical antenna 104 in FIG. 3D is collapsible to facilitateinsertion through narrow openings and lumens and has a sufficientelasticity to regain its shape inside the target vein. In oneembodiment, the diameter of antenna 104 is larger than the diameter ofthe vein lumen. This causes at least a portion of antenna 104 to comeinto physical contact with the wall of the target lumen. However,microwave energy delivery does not necessary need a perfect contact withtarget tissue. Hence embodiments of antenna 104 may be used whereinantenna 104 delivers microwave energy to a portion of the target veineven when antenna 104 does not contact that portion of the target vein.

FIGS. 9A and 9B show a method of transurethral treatment of an internalurethral sphincter for treating stress urinary incontinence (SUI). InFIG. 9A, microwave energy is delivered to the internal urethralsphincter to achieve therapeutic collagen denaturation. In FIG. 9A, amicrowave device 100 comprising an antenna 104 is introduced via atrans-urethral approach into the urinary system. Any suitable antenna104 design disclosed herein may be used for the embodiment in FIGS. 9Aand 9B. In one embodiment, antenna 104 is a monopole antenna with orwithout any shaping element 114. Antenna 104 is positioned such that itis in the vicinity of the internal urethral sphincter as shown in FIG.9A. Antenna 104 may comprise a steering or deflecting modality to changethe orientation of antenna 104 relative to coaxial cable 102. In oneembodiment, antenna 104 is introduced through a sheath comprising asteering or deflecting modality such as one or more pull wires. Thissteering or deflecting modality may be used to position antenna 104 atvarious points in the urinary system to deliver microwave energy tointernal urinary sphincter. Microwave device 100 may comprise a bentregion such that antenna 104 is oriented at an angle relative to coaxialcable 102. Also, microwave device 100 may be twisted as shown in FIG. 9Band/or advanced distally and/or withdrawn proximally to further positionantenna 104 at various points in the urinary system to deliver microwaveenergy to internal urinary sphincter. In an alternate embodiment,antenna 104 is positioned substantially at the center of a lumen or apassage of the urinary system and is used to treat the desired targettissue without direct physical contact of antenna 104 with the targettissue. In such embodiments, the desired clinical effect may be obtainedby delivering microwave energy only once with antenna 104 at a firstposition and thereafter re-delivering microwave energy with antenna 104at a second position. Antenna 104 is used to transmit controlledmicrowave energy to create controlled heating in one or more regions ofthe internal urinary sphincter. In one embodiment, this heating iscarried out at a lower temperature such that there is minimal or no celldeath in the internal urinary sphincter. The heating denatures collagenin the internal urinary sphincter. This denaturation may be carried outat multiple sites by re-positioning antenna 104 or may be carried outwithout re-positioning antenna 104. The collagen denaturation may beused to create firmer tissue that has an increased resistance to theeffects of heightened intra-abdominal pressure, which in turn reduces oreliminates SUI episodes. Any of the methods and devices disclosed hereinmay be used along with a surface cooling modality to cool the surface ofa tissue that is being treated. This allows the surface of the tissue toremain relatively unchanged while microwave energy is delivered tocreate a desired therapeutic effect in deeper regions of the tissue. Forexample, in FIG. 9A, a surface cooling modality may be used to protectthe surface of the lumen of the urinary tract while delivering microwaveenergy to deeper tissues such as the internal urinary sphincter.

In FIG. 9A, the method can be performed under local anesthesia in anoutpatient or office setting. Such methods are especially useful fortreating SUI due to hypermobility in women who have failed conservativecare and who do not desire or are not eligible for surgical therapy.

Since the devices disclosed herein may be designed as low-profile (lessthan 6 F), flexible devices, the devices may be used for treating SUI inboth male as well as female patients. Rigid and larger profile devicesfor collagen denaturation in the prior art are restricted to use inwomen because of their short and relatively straight urethra. However,the use of such prior art devices in male patients is difficult becausethe male urethra is longer and much less straight.

Methods similar to those shown in FIGS. 9A and 9B that involve thedelivery of microwave energy to cause controlled heating of tissue mayalso be used to treat other disorders of anatomical lumens. Examples ofsuch disorders of anatomical lumens include, but are not limited to:gastroesophageal reflux disease and fecal incontinence. In oneembodiment, a device or method disclosed herein may be used for deepertissue heating to cause tissue shrinkage for treating conditions such asfecal incontinence, GERD, urinary incontinence, etc. Such deeper heatingmay be carried out with the device placed within the lumens or otherbodily cavities.

FIG. 9C shows a method embodiment of transurethral treatment of aninternal urethral sphincter for treating stress urinary incontinence(SUI) by an energy delivery device cooperating with a positioningelement. In FIG. 9C, antenna 104 is similar to antenna 104 in FIGS. 9Aand 9B. The shaft of microwave device 100 comprises a microwavetransmission line such as a coaxial cable 102 and a lumen through whichone or more device or fluids may be passed. In FIG. 9C, microwave device100 is introduced by a trans-urethral approach into the urinary tractsuch that antenna 104 is positioned in the vicinity of the internalurethral sphincter. Thereafter, a positioning device 138 is passedthrough the lumen of shaft 102. Thereafter, a positioning element 140located at the distal region of positioning device 138 is deployed inthe urinary bladder. In the embodiment shown in FIG. 9C, positioningelement 140 in its deployed configuration has a width that is greaterthan the width of the urethra but less than the width of the urinarybladder such that positioning element 140 in its deployed configurationis lodged in the urinary bladder. Thereafter, positioning device 138 ispulled in the proximal direction such that positioning element 140 ispositioned against the internal urethral orifice. Thus, by feeling theforces experiences when positioning device 138 is pulled, the locationof the internal urethral orifice can be easily determined without usingany imaging modality. Positioning element 140 positioned against theinternal urethral orifice is then used to position antenna 104accurately at the desired position. In one embodiment, antenna 104 islocated between tissue and positioning element 140. In this embodiment,positioning element 140 may be used to press antenna 104 against tissue.Positioning element 140 may comprise a cooling modality to cool thesurface of tissue. Positioning element 140 is controllably deployablefrom a collapsed, low-profile configuration to a deployed,larger-profile configuration. Thus positioning element 140 may be anon-compliant, semi-compliant or a compliant balloon, an umbrella-likestructure, elastic or super-elastic or shape memory structures,structure comprising one or more bendable splines, etc. Antenna 104 maybe repositioned if necessary to delivery energy to multiple sites in thetarget tissue. After a procedure is completed, positioning element isconverted to a collapsed, low-profile configuration and microwave device100 and positioning device 138 are both removed from the anatomy.

FIG. 9D shows a method embodiment of transurethral treatment of aninternal urethral sphincter for treating stress urinary incontinence(SUI) by an energy delivery device with an antenna that simultaneouslydelivers energy to a larger volume of tissue. In FIG. 9D, antenna 104comprises a radiating element 112 and one or more shaping elements 114.In one embodiment, antenna 104 is used to generate a microwave fieldthat envelopes a majority of the internal urethral sphincter. Althoughantenna 104 may be repositioned if necessary after a first energydelivery, in this embodiment, antenna 104 is designed to create thedesired clinical effect through energy delivery from a single site.

FIG. 10A shows an embodiment of a method for treating Benign ProstaticHyperplasia (BPH) by an energy delivering device. BPH is a benignenlargement of the prostate i.e. an increase in size of the prostateseen in middle-aged and elderly men. The enlarged prostate compressesthe urethral canal and causes partial, or sometimes virtually complete,obstruction of the urethra. This in turn interferes with the normal flowof urine. Thus BPH may lead to symptoms of urinary hesitancy, frequenturination, increased risk of urinary tract infections and urinaryretention. BPH may be treated by reducing the volume of the prostate.FIG. 10A illustrates a method of ablating prostate tissue to reduce thevolume of the prostate. In FIG. 10A, a trans-rectal ultrasound probe 142is used to visualize the anatomy and/or a microwave device 100. Antenna104 of microwave device 100 is inserted into prostate tissue through thewall of the rectum. The distal end of microwave device 100 may comprisea cutting or penetrating edge. The BPH treatment procedure may besimilar to a trans-rectal prostate biopsy procedure by replacing thebiopsy device such as a biopsy needle with microwave device 100.

In one method embodiment, the rectal area is cleaned and a numbing gelis applied. Thereafter, a thin ultrasound probe 142 is inserted into therectum. In one embodiment, ultrasound probe 142 comprises a 5.0 to 7.5MHz transducer. Trans-rectal ultrasonography is then used to image theprostate. The ultrasonography is used to identify one or more of: thesite of penetration of microwave device 100, the one or more areas thatneed to be anesthetized with an anesthetic injection and the one or moresites of ablation. Trans-rectal ultrasonography is thereafter used toguide antenna 104 to a first desired location. Thereafter, ablationenergy is delivered by antenna 104. A single area or multiple areas ofthe prostate may be ablated by repositioning antenna 104 and deliveringmicrowave energy. The protocol for deciding the number and location ofprostate areas to be ablated may be similar to protocol for deciding thenumber and location of prostate areas for prostate needle biopsy. Forexample, protocols similar to five-region, eight systematic coretemplate and the 11-multisite biopsy protocols may be used for ablatingthe prostate.

Antenna 104 in FIG. 10A may comprise a radiating element 112 and one ormore shaping elements 114. Alternately, one or more shaping elements 114may be introduced through a separate device or a separate introductionpath to shape the microwave energy profile generated by antenna 104. Inone such embodiment, antenna 104 comprises a radiating element 112 andis introduced trans-rectally into the prostate while one or more shapingelements 114 are introduced in the urethral lumen. In another suchembodiment, antenna 104 comprises a radiating element 112 and isintroduced trans-rectally or trans-urethrally into the prostate whileone or more shaping elements 114 are located on a separate device thatis introduced trans-rectally into the prostate. Microwave device 100 maybe mechanically coupled to ultrasound probe 142 or may be mechanicallyindependent from ultrasound probe 142.

In alternate method embodiments, one or more regions of the prostate maybe accessed through the urethra, or through the space between the anusand scrotum (perineum).

FIG. 10B shows an embodiment of a method for treating Benign ProstaticHyperplasia (BPH) by an energy delivering device inserted through theurethral lumen. FIG. 10B illustrates a method of ablating prostatetissue to reduce the volume of the prostate. In FIG. 10B, a trans-rectalultrasound probe may be used to visualize the anatomy and/or a microwavedevice 100. Antenna 104 of microwave device 100 is inserted intoprostate tissue through the wall of the urethra. The distal end ofmicrowave device 100 may comprise a cutting or penetrating edge. One ormore regions of microwave device 100 may be bent or curved or may becontrollably deflectable to facilitate insertion of antenna 104 intoprostate tissue.

In one method embodiment, ultrasonography may be used to identify one ormore of: the site of penetration of microwave device 100, the one ormore areas that need to be anesthetized with an anesthetic injection andthe one or more sites of ablation. An imaging modality such astrans-rectal ultrasonography, cystoscopy or fluoroscopy may be used toguide antenna 104 at a first desired location. Thereafter, ablationenergy is delivered by antenna 104. A single area or multiple areas ofthe prostate may be ablated by repositioning antenna 104 and deliveringmicrowave energy.

Antenna 104 in FIG. 10B may comprise a radiating element 112 and one ormore shaping elements 114. Alternately, one or more shaping elements 114are introduced through a separate device or a separate introduction pathto shape the microwave energy profile generated by antenna 104. In onesuch embodiment, antenna 104 comprises a radiating element 112 and isintroduced trans-urethrally into the prostate while one or more shapingelements 114 are introduced trans-rectally. In another such embodiment,antenna 104 comprises a radiating element 112 and is introducedtrans-urethrally into the prostate while one or more shaping elements114 are located on a separate device that is introduced trans-urethrallyinto the prostate.

FIG. 10C shows an embodiment of a method for treating Benign ProstaticHyperplasia (BPH) by an energy delivering device inserted in theurethral lumen. FIG. 10C illustrates a method of ablating prostatetissue to reduce the volume of the prostate. In FIG. 10C, suction isapplied inside the lumen of the urethra to collapse the urethra aroundantenna 104. Thus, the urethral lumen wall comes into contact with orcomes in the vicinity of antenna 104. Thereafter, microwave energy isdelivered by antenna 104 to achieve the desired therapeutic outcome.Thus, the method is non-invasive. In FIG. 10C, antenna 104 may beintroduced under cystoscopic guidance either through a cystoscopicsheath or simple co-introduced along with a cystoscope. In FIG. 10C, atrans-rectal ultrasound probe may be used to visualize the anatomyand/or a microwave device 100. In one embodiment, microwave device 100is positioned at a single location inside the prostatic urethra andmicrowave energy delivery is carried out from this single location.Alternately, antenna 104 may be repositioned one or more times insidethe prostatic urethra. One or more regions of microwave device 100 maybe bent or curved or may be controllably deflectable.

FIGS. 11A-11C illustrate the use of a microwave device with a steerableor deflectable antenna used to treat Gastroesophageal Reflux Disease(GERD). In FIGS. 11A-11C, the orientation of antenna 104 relative to theorientation of the distal region of coaxial cable 102 can be changed byengaging a steering or deflecting mechanism located on microwave device100 or on a sheath that encloses microwave device 100. This steering ordeflecting mechanism (e.g. one or more pull wires) may be used toposition antenna 104 at various points in the digestive system todeliver microwave energy to the smooth muscle of the gastroesophagealjunction. In FIG. 11A, a microwave device 100 e.g. a microwave cathetercomprising an antenna 104 is introduced via a trans-esophageal approachinto the stomach. Any suitable antenna 104 design disclosed herein maybe used for the embodiment in FIGS. 11A. In one embodiment, antenna 104is a monopole antenna with or without any shaping element 114. Inanother embodiment, antenna 104 of FIG. 11A is similar to antenna 104 ofFIG. 1C. Microwave device 100 may be introduced into the stomach underendoscopic guidance with the patient under conscious sedation. Antenna104 is positioned such that it is in the vicinity of the smooth muscleof the gastroesophageal junction as shown in FIG. 11A. Also, microwavedevice 100 may be rotated and/or advanced distally and/or withdrawnproximally to further position antenna 104 at various points in thedigestive system to deliver microwave energy to the smooth muscle of thegastroesophageal junction. Antenna 104 is used to transmit controlledmicrowave energy to create thermal lesions below the mucosa at thegastroesophageal junction. This in turn may be used to create one ormore of the following clinical effects: controlling reflux by inhibitingtransient, inappropriate lower esophageal sphincter (LES) relaxation,increasing postprandial LES pressure and decreasing LES compliance. Asurface cooling modality may be used to protect the surface of themucosa of the gastrointestinal tract while delivering microwave energyto deeper tissues such as the LES.

In FIG. 11B, antenna 104 is moved to a second location in the vicinityof the smooth muscle of the gastroesophageal junction in the greatercurvature of the stomach. This may be done by one or more of: engaging asteering or deflecting mechanism on microwave device 100 or on a sheaththat encloses microwave device 100, rotating microwave device 100,advancing microwave device 100 distally and withdrawing microwave device100 proximally. In FIG. 11C, antenna 104 is moved to a third location inthe vicinity of the smooth muscle of the gastroesophageal junction inthe lesser curvature of the stomach. This may be done by one or more of:engaging a steering or deflecting mechanism on microwave device 100 oron a sheath that encloses microwave device 100, rotating microwavedevice 100, advancing microwave device 100 and withdrawing microwavedevice 100 proximally. Thus, antenna 104 may be used to treat multiplelocations in the gastrointestinal tract to treat GERD.

FIG. 12A shows a method embodiment of using an antenna along with asurface cooling modality to improve the cosmetic appearance of skin. InFIG. 12A, an antenna 104 delivers microwave energy to the skin to heatone or more skin layers. This heating may be carried out at a lowertemperature such that there is minimal or no cell death. In theembodiment shown in FIG. 12A, antenna 104 does not directly contact theskin. Various designs of antennas 104 disclosed herein may be used tothe method in FIG. 12A. The antennas 104 may have a suitable crosssection tailored for a particular application. For example, antennas 104may be designed with a cross sectional areas ranging from 0.5 sq. cm to9 sq. cm. The antenna 104 may be linear such as shown in FIG. 1C or maybe in a bent or curved configuration such as shown in FIG. 3 series. Anysuitable frequency of microwave energy may be used for this applicationand any other applications disclosed herein. A surface cooling modality144 is used to cool the surface of the skin to prevent undesired damageto the superficial skin layers. Examples of suitable surface coolingmodalities 144 include, but are not limited to: inflatable structuresinflated with a cooling fluid, gels or other conformable structures andstructures designed to circulate one or more fluids on the skin surface.In one embodiment, surface cooling modality 144 does not interfere withthe passage of microwave energy. Thus, surface cooling modality 144 maybe an inflatable balloon inflated with a circulating, non-polar coolingfluid. Antenna 104 may be used for volumetric heating of deeper layersof the skin while protecting the epidermis. This may be used tonon-invasively create one or more of the following effects: smootheningskin, tightening skin and contouring skin. This method may also be usedto reduce the appearance of cellulite. This method may also be used toreduce skin dimpling for the thigh and buttock areas. In one embodiment,microwave energy is used to heat the dermis and subcutaneous tissue tocause contraction of collagen fibrils. This may be followed by secondarycollagen synthesis and remodeling to achieve the desired cosmeticeffect. A compression garment may be worn by the patient after thetreatment. The treatment may be carried out in a single treatmentsession or in multiple treatment sessions. In each treatment session, asurface of the skin may be treated by delivering microwave energy inmultiple staggered passes, multiple non-staggered passes or in a singlepass.

Various antenna embodiments disclosed herein may be used to buildablation catheters for treating a variety of electrophysiologicalconditions (e.g. atrial fibrillation, Ventricular Tachycardia,Bradycardia, flutter and other arrhythmias) and for treating heartstructures including, but not limited to walls of the atria or theventricles, valves and the regions surrounding the valves to treatnon-electrophysiological conditions. Antenna 104 may be used to create aseries of ablations in the left atrium to treat atrial fibrillation.Antenna 104 may be used to create long and transmural lesions in theleft atrium. The lesions in the left atrium may be used to imitate aMaze procedure. Antenna 104 may be positioned at various locationsaround the pulmonary vein and used to ablate various locations aroundthe pulmonary vein for electrophysiological isolation of the pulmonaryvein.

Several embodiments of planar antennas 104 are also included in thescope of the invention. Such planar antennas 104 may be used to ablateor otherwise treat planar or non-planar tissue regions. Such planarantennas 104 may comprise single or multiple splines, curves or loops ina generally planar arrangement. Planar antennas 104 may be used forablating a surface such as the surface of organs such as liver, stomach,esophagus, etc. For example, FIG. 13A shows a view of a planar antennaof a microwave ablation device designed for endometrial ablation. InFIG. 13A, microwave ablation device 100 comprises a transmission line(such as a coaxial cable 102) terminating in an antenna 104 at thedistal end of the transmission line. In one embodiment, a singlemicrowave signal is fed to antenna 104 through coaxial cable 102.Antenna 104 generates a microwave field. The near field of the microwavefield generated by antenna 104 is used for endometrial ablation. In FIG.13A, antenna 104 comprises a radiating element in the form of an outerloop 112 and a shaping element in the form of a metallic center loop114. Outer loop 112 and center loop 114 may touch each other whendeployed in the anatomy. In one embodiment, outer loop 112 is acontinuation of the inner conductor of coaxial cable 102. Center loop114 shapes or redistributes the microwave field radiated by outer loop112. It should be noted that there is no direct electrical conductionbetween outer loop 112 and center loop 114. When microwave energy isdelivered through coaxial cable 102 to antenna 104, a first microwavefield is emitted by outer loop 112. The first microwave field interactswith center loop 114. This interaction induces a leakage current oncenter loop 114. The leakage current in turn creates a second microwavefield. The first microwave field and the second microwave field togethercombine to produce a unique shaped microwave field of antenna 104 thatis clinically more useful that the unshaped microwave field generated byan antenna 104 comprising only outer loop 112. Thus the originalmicrowave field is redistributed by the design of center loop 114.Center loop 114 alone is not capable of functioning as an antenna;rather center loop 114 shapes or redistributes the electromagnetic ormicrowave field emitted by outer loop 112 to produce a shaped microwavefield that is clinically more useful. Further, the combination of outerloop 112 and center loop 114 improves the power deposition of antenna104.

In one embodiment, outer loop 112 has no sharp corners. Sharp corners inouter loop 112 may cause the field to concentrate in the vicinity of thesharp corners. In one embodiment, the minimal radius of curvature of acorner in outer loop 112 is at least 0.5 mm. In the embodiment in FIG.13A, the radius of curvature of corner regions 154 and 156 in outer loop112 is about 1 mm+/−0.3 mm.

In one embodiment, antenna 104 has a shape that substantiallyapproximates the shape of the body organ to be ablated. For example,antenna in FIG. 13A has a roughly triangular shape that approximates theshape of the uterine cavity and is especially suited for endometrialablation. The proximal portion of the antenna 104 is directed towardsthe cervix and corner regions 154 and 156 of outer loop 112 are directedtowards the fallopian tubes. However, as mentioned before, microwavethermal ablation does not necessarily require perfect contact with allof the target tissue. Thus antenna 104 is able to ablate all orsubstantially all of the endometrium. The entire endometrium can beablated in a single ablation by antenna 104 having a single microwaveantenna. Thus, repositioning of antenna 104 after an ablation is notneeded. This greatly reduces the amount of physician skill needed forthe procedure. Further, multiple antennas 104 are not needed in ablationdevice 100. A single antenna 104 positioned at a single location is ableto ablate a therapeutically sufficient amount of the endometrium. Thissimplifies the design of ablation device 100.

Further, antenna 104 in the working configuration is generally flat andflexible. The plane of outer loop 112 is substantially parallel to theplane of center loop 114. Thus, the uterine walls experience only slightforces from antenna 104. This in turn reduces or eliminates thedistension of the uterine wall thereby reducing the discomfort to thepatient. This in turn further reduces the anesthesia requirements.Flexible antenna 104 may easily be introduced in a collapsedconfiguration through a small lumen thereby eliminating or minimizingany cervical dilation. This dramatically reduces the discomfort to thepatient consequently significantly reducing the requirement ofanesthesia. This has tremendous clinical advantages since now theprocedure can be performed in the physician's office under localanesthesia.

Further, flat and flexible antenna 104 in FIG. 13A in its deployedconfiguration has an atraumatic distal end in which the distal region ofantenna 104 is wider than the proximal portion of antenna 104. Thisreduces the risk of perforation of the uterus. The flexible nature ofantenna enables antenna 104 to take the natural shape of passage duringintroduction instead of distorting the passage. For example, whenantenna 104 is introduced trans-cervically into the uterus, antenna 104may acquire the shape of introduction passage comprising the vagina,cervical canal and uterine cavity instead of distorting one or more ofthe vagina, cervical canal and uterine cavity.

In one embodiment of a deployed configuration of antenna 104 as shown inFIG. 13A, the length of outer loop 112 measured along the outer loop 112from the distal end of coaxial cable 102 until the distal end 158 ofouter loop 112 is about three quarters of the effective wavelength atthe 915 MHz ISM band. The effective wavelength is dependent on themedium surrounding the antenna and the design of an antenna dielectricon the outer loop 112. The design of the antenna dielectric includesfeatures such as the type of dielectric(s) and thickness of thedielectric layer(s). The exact length of the outer loop 112 isdetermined after tuning the length of outer loop 112 to get goodimpedance matching. The length of the outer loop 112 in one embodimentis 100+/−15 mm. In one embodiment, the width of deployed outer loop 112is 40+/−15 mm and the longitudinal length of deployed outer loop 112measured along the axis of coaxial cable 102 is 35+/−10 mm. In theembodiment shown in FIG. 13A, distal end 158 of outer loop 112 ismechanically connected to the distal end of coaxial cable 102 by anelongate dielectric piece 160.

In one embodiment, the proximal portion of outer loop 112 is designed tobe stiffer and have greater mechanical strength than the distal portion.In the embodiment shown in FIG. 13A, this may be achieved by leavingoriginal dielectric material 110 of coaxial cable 102 on the proximalportion of outer loop 112. In an alternate embodiment, this is achievedby coating the proximal portion of outer loop 112 by a layer of antennadielectric.

In the embodiment shown in FIG. 13A, the cross sectional shape of outerloop 112 is not uniform along the entire length of outer loop 112. Inthis embodiment, the proximal portion of outer loop 112 is acontinuation of the inner conductor of coaxial cable 102. This portionhas a substantially circular cross section. A middle portion of outerloop 112 has a substantially flattened or oval or rectangular crosssection. The middle portion may be oriented generally perpendicular tothe distal region of coaxial cable 102 in the deployed configuration.The middle portion of outer loop 112 is mechanically designed to bend ina plane after deployment in the anatomy. This in turn ensures that thedistal most region of ablation device 100 is atraumatic and flexibleenough to conform to the target tissue anatomy. This helps in the properdeployment of outer loop 112 in the uterus. In one embodiment, themiddle portion of outer loop 112 is a continuation of inner conductor ofcoaxial cable 102 and is flattened. In one embodiment, the distal mostportion of outer loop 112 is a continuation of inner conductor ofcoaxial cable 102 and is non-flattened such that it has a circular crosssection.

One or more outer surfaces of outer loop 112 may be covered with one ormore layers of antenna dielectrics 116. One or more outer surfaces ofcenter loop 114 may be covered with one or more layers of antennadielectrics 116. The thickness and type of antenna dielectric materialalong the length of outer loop 112 is engineered to optimize themicrowave field shape. In one embodiment shown in FIG. 13A, everyportion of outer loop 112 is covered with some antenna dielectricmaterial such that no metallic surface of outer loop 112 is exposed totissue. Thus, in the embodiment of FIG. 13A, outer loop 112 is able totransmit a microwave field into tissue, but unable to conductelectricity to tissue. Thus, in the embodiment of FIG. 13A, there is noelectrical conduction and no conductive path between outer loop 112 andcenter loop 114 even though outer loop 112 and center loop 114 mayphysically touch each other when deployed in the anatomy. Examples ofdielectric materials that can be used as antenna dielectrics in one ormore embodiments disclosed herein include, but are not limited to EPTFE,PTFE, FEP and other floropolymers, Silicone, Air, PEEK, polyimides,cyanoacrylates, epoxy, natural or artificial rubbers and combinationsthereof. In the embodiment of FIG. 13A, the antenna dielectric 116 onthe proximal portion of outer loop 112 is a continuation of thedielectric 110 of coaxial cable 102. There may be an additional layer ofa stiffer antenna dielectric 116 over this later of antenna dielectric116. In the embodiment of FIG. 13A, the dielectric on the middle portionof outer loop 112 is a silicone layer with or without impregnated air ora silicone tube enclosing a layer of air. In the embodiment of FIG. 13A,the dielectric on the distal most portion of outer loop 112 is asilicone layer with or without impregnated air or a silicone tubeenclosing a layer of air or EPTFE. The thickness of an antennadielectric on any portion of outer loop 112 may vary along the length ofouter loop 112. Further, the crossection of an antenna dielectric on anyportion of outer loop 112 may not be symmetric. The variousconfigurations of the antenna dielectric are designed to achieve thedesired ablation profile as well as achieve the desired impedancematching or power efficiency. In an alternate embodiment, entire outerloop 112 is covered with silicone dielectric. In one such embodiment,the layer of silicone used to coat the distal most portion of outer loop112 may be thinner than the layer of silicone used to coat the middleportion of outer loop 112. The thinner silicone dielectric compensatesfor the lower field strength that normally exists at the distal mostportion of a radiating element such as outer loop in FIG. 13A. Thus, themicrowave field is made more uniform along the length of outer loop 112.In one device embodiment, outer loop 112 is made of a metallic materialand the circumference of the metallic material of the distal region ofouter loop 112 is more than the circumference of the metallic materialof the middle portion of outer loop 112. This causes the siliconedielectric to stretch more at the distal portion than at the middleportion of outer loop 112. This in turn generates a thinner layer ofantenna dielectric at the distal portion of outer loop 112 than at themiddle portion of outer loop 112. In another embodiment, entire outerloop 112 is made from a single length of metallic wire of a uniformcrossection. In this embodiment, a tubular piece of silicone dielectricof varying thickness is used to cover outer loop 112. The tubularsilicone dielectric is used to cover the distal and middle portions ofouter loop 112 such that the layer of silicone dielectric is thinnernear the distal portion and thicker near the middle portion of outerloop 112.

In FIG. 13A, the shape of outer loop 112 is different from the shape ofcenter loop 114. Further, in FIG. 13A, outer loop 112 and center loop114 are substantially planar and the plane of outer loop 112 issubstantially parallel to the plane of center loop 114. Further, in FIG.13A, both outer loop 112 and center loop 114 are non-linear.

FIG. 13B shows a section of ablation device 100 of FIG. 14A through thedistal end of coaxial cable 102. In FIG. 13B, the identity of coaxialcable 102 ends at the distal end of outer conductor 106. The outerjacket 118 ends a small distance proximal to the distal end of outerconductor 106. Inner conductor 108, cladding 120 and dielectric material110 extend distally from the distal end of outer conductor 106 intoantenna 104. Two proximal ends of center loop 114 are electricallyconnected to two regions on the outer conductor 106. In one embodiment,the two proximal ends of center loop 114 are electrically connected todiametrically opposite regions on the distal end of outer conductor 106.In one embodiment, the two proximal ends of center loop 114 are solderedto the distal end of outer conductor 106. In another embodiment, the twoproximal ends of center loop 114 are laser welded to the distal end ofouter conductor 106. The two proximal ends of center loop 114 may beconnected to the distal end of outer conductor 106 in variousconfigurations including, but not limited to lap joint and butt joint.In an alternate embodiment, at least one of the two proximal ends ofcenter loop 114 is not connected to the distal end of outer conductor106. For example, at least one of the two proximal ends of center loop114 may be electrically connected to a region of outer conductor 106that is proximal to the distal end of outer conductor 106.

In a method embodiment, when ablation device 100 is used for endometrialablation, antenna 104 of FIG. 13A generates a substantially uniformmicrowave field that is more concentrated in the center of the uterusand is less concentrated towards the cornual regions and towards thecervix. Thus, the depth of ablation generated by antenna 104 is deeperin the center of the uterus and is less deep towards the cornual regionsand towards the cervix. Such a profile is clinically desired forimproved safety and efficacy. In one embodiment, the ablation profile isshaped to ablate a majority of the basalis layer of the uterineendometrium. In one embodiment, center loop 114 is made of a round orflat wire. Examples of flat wires that can be used to make center loop114 are flat wires made of Ag or Au plated Nitinol or stainless steelwith a cross sectional profile of about 0.025″×about 0.007″. Such a loopshaped shaping element does not act as a shield for the microwave field.This non-shielding action is visible in the SAR pattern in FIG. 14B. InFIG. 14B, there is no sharp drop in the microwave field intensity pastcenter loop 114. In the embodiment of FIG. 13A, center loop 114 isroughly oval in shape. Two proximal ends of center loop 114 areelectrically attached to two circumferentially opposite regions of theouter conductor of coaxial cable 102. In the embodiment of FIG. 13A, thewidth of center loop 114 is 13+/−5 mm and the length of center loop 114is 33+/−8 mm. When ablation device 100 is used for endometrial ablation,outer loop 112 and center loop 114 both contact the endometrial tissuesurface.

Center loop 114 may be mechanically independent from outer loop 112 ormay be mechanically attached to outer loop 112. In the embodiment shownin FIG. 13A, center loop 114 is mechanically independent from outer loop112 and lies on one side of outer loop 112. In an alternate embodiment,a portion of center loop 114 passes through the interior of outer loop112. In an alternate embodiment, a portion of center loop 114 ismechanically connected to outer loop 112. This may be done for example,by using an adhesive to connect a portion of center loop 114 to outerloop 112. In an alternate embodiment, one or more portions of centerloop 114 are mechanically connected to one or more portions of outerloop 112 by one or more flexible attachments.

Parts of center loop 114 may or may not be covered by one or more layersof antenna dielectric materials 116. In the embodiment of FIG. 13A, oneor more or all metallic surfaces of center loop 114 are exposed to thedevice environment.

Portions of outer loop 112 and center loop 114 may be made from one ormore of lengths of metals such as copper, Nitinol, aluminum, silver orany other conductive metals or alloys. One or more portions of outerloop 112 and center loop 114 may also be made from a metallized fabricor plastics.

FIGS. 14B and 14C show the front and side views respectively of the SARprofile generated by an antenna with a center loop similar to theantenna of FIG. 13A. In the embodiment in FIG. 14B, the distal end ofouter loop 112 is mechanically and non-conductively attached to a regionof outer loop 112 proximal to the distal end of outer loop 112. Thus,outer loop 112 has a substantially linear proximal region and a loopeddistal region. In one embodiment, the looped distal region may besubstantially triangular in shape as shown in FIG. 14B. Outer diameterof antenna dielectric 116 on the proximal region of outer loop 112 maybe larger than or substantially the same as the outer diameter ofantenna dielectric 116 on the looped distal region of outer loop 112.Antenna dielectric 116 on the looped distal region of outer loop 112 maybe a layer of silicone of varying thickness. Outer loop 112 may be madeof a silver or gold clad metal such as Nitinol. Center loop 114 may bemade of a silver or gold clad metal such as Nitinol. In the embodimentshown in FIGS. 14B and 14C, center loop 114 is not covered with anyantenna dielectric 116. Thus the metallic surface of center loop 114 maybe exposed to the surrounding. Outer loop 112 and center loop 114 mayphysically touch each other when deployed in the anatomy as shown inFIG. 14E. In FIG. 14B, the microwave field is shaped such that theablation at the center of antenna 104 will be deeper than the ablationat the corners of antenna 104. This is clinically desirable forendometrial ablation. Also, FIGS. 14B and 14C show that the microwavefield volumetrically envelops entire antenna 104. Also, FIGS. 14B and14C show that the microwave field is substantially bilaterallysymmetric. FIG. 14E shows the front view of the SAR profile generated byantenna 104 of FIG. 14B without center loop 114. The microwave effect ofshaping element 114 in FIG. 14B can be seen by comparing FIG. 14B toFIG. 14E. FIG. 14E shows a first unshaped field that is not shaped byshaping element 114. When the antenna 104 comprises a shaping element114 as shown in FIG. 14B, the antenna generates a shaped microwave fieldas shown in FIG. 14B. It should be noted that in FIGS. 14B and 14C, theshaped microwave field is more uniformly distributed over a wider areaof the endometrium than in FIG. 14E. In FIG. 14E, the unshaped microwavefield is more concentrated at the distal end of coaxial cable 102. Amore uniformly distributed, shaped microwave field such as in FIGS. 14Band 14E is clinically desirable for endometrial ablation. Further whenantenna 104 of FIG. 14B is used for endometrial ablation, the microwavefield is distributed over a wider area of the endometrium that themicrowave field generated by antenna 104 of FIG. 14E. This can be seenby comparing the SAR profile distal to the distal end of coaxial cable102 in FIGS. 14B and 14C to the SAR profile distal to the distal end ofcoaxial cable 102 in FIG. 14E. Further, in FIG. 14E, a portion of theunshaped microwave field extends to a significant distance proximal tothe distal end of coaxial cable 102. In FIGS. 14B and 14E, aninsignificant portion of the microwave field extends proximally to thedistal end of coaxial cable 102. Thus the microwave field profile ofFIGS. 14B and 14C is advantageous over the microwave field profile ofFIG. 14G since it limits collateral damage to healthy tissue. Thus thepresence of center loop 114 shapes the microwave field such that themicrowave field is more distributed. In absence of center loop 114, themicrowave field interacts with an element of transmission line 102 suchas the outer conductor of a coaxial cable. This results in anon-desirable profile of the microwave field e.g. a concentrated fieldaround the distal end of the transmission line 102 as shown in FIG. 14E.This interaction can also cause backward heating of coaxial cable 102that may lead to collateral damage of healthy tissue. Further, thecombination of outer loop 112 and center loop 114 creates a more robustantenna 104 wherein the performance of antenna 104 is less affected bydistortions during clinical use. Also, FIGS. 14B and 14C show that themicrowave field volumetrically envelops entire antenna 104.

Further, the SAR profile of FIG. 14B demonstrates that the entireuterine endometrium can be ablated in a single ablation. Thus thephysician does not need to reposition antenna 104 after a firstendometrial ablation. This novel aspect of the device and proceduregreatly reduces the amount of time needed for the procedure and alsoreduces the procedure risks and physician skill requirements. In theembodiments disclosed herein, a combination of direct microwavedielectric heating and thermal conduction through tissue is used toachieve the desired therapeutic effect. The thermal conduction evens outany minor variations in the microwave field and enables the creation ofa smooth, uniform ablation. Further, the SAR profile of FIGS. 14B and14C demonstrates that antenna 104 is capable of ablating an entirevolume surrounding antenna 104 not just ablating between the surfaces ofouter loop 112 and center loop 114. Further, the SAR profile of FIGS.14B and 14C demonstrates that antenna 104 is capable of ablating atissue region without leaving any “gaps” of unablated tissue within thattissue region. Further, the SAR profile of FIGS. 14B and 14Cdemonstrates that the entire microwave field generated by antenna 104 isused for ablation. The entire microwave field comprises the microwavefield around outer loop 112, the microwave field around center loop 114,the microwave field between outer loop 112 and center loop 114 and thefield within center loop 114. Further, the SAR profile of FIGS. 14B and14C demonstrates that the microwave field is located all around outerloop 112 and is not shielded or reflected by center loop 114. Thuscenter loop 114 does not act as a shield or reflector in the embodimentshown in FIGS. 14B and 14C.

Various embodiments of antenna 104 may be designed to generate a varietyof shapes of SAR and/or the ablation profile. For example, antennas 104may be designed to generate substantially square, triangular,pentagonal, rectangular, round or part round (e.g. half round, quarterround, etc.), spindle-shaped or oval SARs or ablation patterns.

FIG. 14D shows the simulated return loss of an ablation device withantenna 104 of FIG. 14B. The simulated return loss shows good matching(about −11 dB) at 915 MHz. FIG. 14F shows the simulated return loss ofan ablation device with an antenna of FIG. 14E. The simulation shows areturn loss of about −7.5 dB at 915 MHz. Thus, the presence of centerloop 114 also improves the matching and increases the power efficiency.In the presence of center loop 114, microwave power is delivered moreefficiently to the tissue and not wasted as heat generated withinablation device 100.

Shaping element 114 also increases the frequency range (bandwidth) overwhich antenna 104 delivers an acceptable performance. If the graphs inFIG. 14D and 14F are compared, at a cutoff of −10 dB, the acceptablefrequency range in the embodiment containing shaping element 114 is morethan 0.52 GHz (spanning from approximately 0.88 GHz to more than 1.40GHz). The acceptable frequency range in the comparable embodiment ofFIG. 14E without shaping element 114 is only about 0.18 GHz (spanningfrom approximately 0.97 GHz to approximately 1.15 GHz). Thus in thefirst case, a larger frequency range (bandwidth) is available over whichantenna 104 delivers an acceptable performance. This in turn allows fora design of antenna 104 wherein minor distortions of antenna 104 duringtypical clinical use or due to minor manufacturing variations do notsignificantly affect the performance of antenna 104.

FIGS. 14G and 14H show the front and side views respectively of the SARprofile generated by an antenna with a center loop similar to theantenna of FIG. 14B. The general construction of the embodiment in FIG.14G is similar to the general construction of the embodiment in FIG.14B. However, in FIG. 14G, the radius of curvature of the two distaledges of the looped distal region of outer loop 112 is more than thecorresponding radius of curvature in FIG. 14B. Further, the length ofthe substantially linear proximal region of outer loop 112 is less thanthe corresponding length in FIG. 14B. Also, the design of antennadielectric 116 on antenna 104 in FIG. 14G is different from the designof antenna dielectric 116 on antenna 104 in FIG. 14B. In one embodiment,antenna dielectric 116 on the proximal region of outer loop 112 is madeof a layer of PEEK over a layer of EPTFE. The PEEK layer increases themechanical strength of the proximal region of outer loop 112. In thisembodiment, the antenna dielectric 116 on the looped distal region ofouter loop 112 is silicone of varying thickness. The thickness of thesilicone antenna dielectric 116 on the more proximal portion of thelooped distal region of outer loop 112 may be more than the thickness ofsilicone antenna dielectric 116 on the more distal portion of the loopeddistal region of outer loop 112. Outer loop 112 may be made of a silveror gold clad metal such as Nitinol. Center loop 114 may be made of asilver or gold clad metal such as Nitinol. In the embodiment shown inFIGS. 14B and 14C, center loop 114 is not covered with any antennadielectric 116. Thus the metallic surface of center loop 114 may beexposed to the surrounding. Outer loop 112 and center loop 114 mayphysically touch each other when deployed in the anatomy as shown inFIG. 14C. The clinical advantages of the shape of the SAR profile ofantenna 104 in FIGS. 14G and 14H are similar to the clinical advantagesof the SAR profile of antenna 104 in FIGS. 14B and 14C.

FIGS. 14I and 14J show two alternate embodiments of shapes of microwaveantenna 104 of ablation device 100. In FIGS. 14I and 14J, center loop114 is not shown. In FIG. 14I, microwave antenna 104 is roughly diamondshaped. The distal most region of microwave antenna 104 measured alongthe axis of coaxial cable 102 comprises a smooth corner. The microwaveantenna 104 in this embodiment is pre-shaped to form the shape as shownin FIG. 14I. Such a microwave antenna 104 can be collapsed to enableinsertion of microwave antenna 104 in a collapsed, low-profileconfiguration though a lumen of a device. In FIG. 14I, microwave antenna104 is sized and shaped such that when antenna 104 is deployed in theuterine cavity, the distal most region of microwave antenna 104 measuredalong the axis of coaxial cable 102 is pushed by the uterine fundus andflattened to achieve the configuration as shown by the dashed lines.Thus microwave antenna 104 is converted to a roughly triangular shapethat is suited for endometrial ablation. In FIG. 14J, the distal mostregion of microwave antenna 104 measured along the axis of coaxial cable102 comprises a smooth arc or curve. The microwave antenna 104 in thisembodiment is pre-shaped to form the shape as shown in FIG. 14J. Such amicrowave antenna 104 can be collapsed to enable insertion of microwaveantenna 104 in a collapsed, low-profile configuration though a lumen ofa device. In FIG. 14J, microwave antenna 104 is sized and shaped suchthat when it is deployed in the uterine cavity, the distal most regionof microwave antenna measured along the axis of coaxial cable 102 ispushed by the uterine fundus and flattened to achieve the configurationas shown by the dashed lines. Thus microwave antenna 104 is converted toa roughly triangular shape that is suited for endometrial ablation. Inan alternate embodiment, microwave antenna 104 has elastic,super-elastic or shape memory ability. In this embodiment, microwaveantenna 104 regains its shape after deployment in the uterine cavitythrough a lumen of a device. FIG. 14K shows the substantially circularcrossection of microwave antenna 104 through plane 14K-14K. FIG. 14Lshows two alternate crossections of microwave antenna 104 through plane14L-14L. In FIG. 14L, one alternate crossection is rectangular while theother alternate crossection is oval.

FIGS. 14M-14O show various embodiments of ablation devices 100comprising roughly triangular shaped microwave antennas 104. In FIG.14M, ablation device 100 comprises a coaxial cable 102, an outer loop112 and a center loop 114. Ablation device 100 further comprises anelongate metallic conductor 168 similar to elongate metallic conductor168 of FIG. 14R. The proximal end of elongate metallic conductor 168 iselectrically connected to the distal end of outer conductor 106 ofcoaxial cable 102. The distal end of metallic conductor 168 isnon-conductively attached to the distal end 158 of outer loop 112.Metallic conductor 168 confers mechanical stability to the outer loop112 as well as shapes the microwave field. In FIG. 14N, ablation device100 comprises a coaxial cable 102, an outer loop 112 and a center loop114. In this embodiment, a region of outer loop 112 adjacent to thedistal end of coaxial cable 102 is electrically shorted to anotherregion of outer loop 112 adjacent to the distal end of coaxial cable102. In FIG. 14O, ablation device 100 comprises a coaxial cable 102, anouter loop 112 and a center loop 114. In this embodiment, regions ofouter loop 112 are electrically isolated from other regions of outerloop 112. Thus, no two regions of outer loop 112 are conductivelyconnected.

FIGS. 14P-14R show various alternate embodiments of center loop 114.Center loop 114 in FIGS. 14P-14R is made of Ag or Au plated Nitinol orstainless steel. Center loop 114 may or may not be pre-shaped. Thecrossection of center loop 114 may be circular or rectangular or oval.Center loop 114 may be multi-stranded. In FIG. 14P, center loop 114 isroughly oval in shape and has a width of 13+/−5 mm and a length of about35+/−8 mm. In FIG. 14Q, center loop 114 is roughly oval in shape and hasa width of 13+/−5 mm and a length of about 27.5+/−8 mm. In FIG. 14R,center loop 114 is roughly oval in shape and has a width of 13+/−5 mmand a length of about 35+/−8 mm. In FIG. 14R, ablation device 100further comprises one or more additional elongate metallic conductors168 electrically connected to the distal end of outer conductor 106. Thedistal end of elongate metallic conductor 168 is connected to a regionof antenna 104 to confer mechanical stability to antenna 104 as well asto shape the microwave field. In a one embodiment, the distal end ofelongate metallic conductor 168 is connected to a region of antenna 104by a non-conductive connection. Various antennas 104 may be designedusing a combination of various elements disclosed herein. Variousantennas 104 may be designed using any combination of a radiatingelement 112 disclosed herein and a shaping element 114 disclosed herein.For example, a design of outer loop 112 from FIGS. 14I-14O may becombined with a design of center loop 114 in FIGS. 14P-14R to createvarious antennas 104.

FIGS. 14S and 14T show two configurations of a mechanically deployableantenna. In FIG. 14S, antenna 104 comprises an outer loop 112 and acenter loop 114. In FIG. 14S, antenna 104 is in a non-workingconfiguration. Antenna 104 in this embodiment is user deployable byengaging a mechanical deployment system. The mechanical deploymentsystem in the embodiment in FIGS. 14S and 14T is a pullable andreleasable pull wire 170 attached to a region of outer loop 112. Pullwire 170 may be made of a metallic or non-metallic e.g. polymericmaterial. When pull wire 170 is pulled along the proximal direction,outer loop 112 is distorted. The distortion is such that antenna 104achieves a working configuration as shown in FIG. 14T. Such anembodiment wherein a pull wire 170 is used to convert antenna 104 from anon-working configuration to a working configuration is advantageoussince presence of tissue forces are not required for the properdeployment of antenna. This allows the antenna 104 to be made stiffer.One or more pull wires 170 may be attached to one or more regions ofantenna 104 to controllably modify the orientation of antenna 104relative the axis of the distal end of coaxial cable 102. This may beused to position antenna 104 relative to a target tissue in a desiredorientation while performing e.g. a laparoscopic procedure. Further, amechanical deployment system allows the user to get a feedback about theproper deployment of antenna 104. This eliminates the necessity of apost-deployment visualization of antenna 104 to confirm properdeployment. For example, the mechanical deployment system as shown inFIGS. 14S and 14T allows the user to get a tactile feedback about theproper deployment of antenna 104 by the forces the user experienceswhile engaging pull wire 170. In another example, the mechanicaldeployment system as shown in FIGS. 14S and 14T allows the user tovisually observe the extent of displacement of pull wire 170 which iscorrelated to the extent of deployment of antenna 104.

FIG. 14U shows a longitudinally un-constrained and laterallyun-collapsed configuration of an embodiment of a microwave antenna. InFIG. 14U, ablation device 100 comprises an antenna 104 comprising anouter loop 112 and a metallic center loop 114. Outer loop 112 in thisconfiguration is in a more oval shape. The distal end of outer loop 112is connected to a proximal portion of outer loop 112 by anon-electrically conducting connection. The maximum lateral widthdimension of antenna 104 is about 2.7 cm. The lateral width of centerloop 114 may be 1.6 cm+/−0.6 cm and the longitudinal length of centerloop 114 may be about 3.5 cm+/−1 cm.

FIG. 14V shows a longitudinally constrained and laterally un-collapsedworking configuration of the embodiment of a microwave antenna shown inFIG. 14U. In FIG. 14V, an external force is used to distort the distalmost portion of antenna 104. In FIG. 14V, a finger was used to distortthe distal most portion of antenna 104 to change outer loop 112 from amore oval shape to a more triangular shape as shown. The maximum lateralwidth dimension of outer loop 112 is now about 3.5 cm. The longitudinallength of antenna 104 from the distal end of coaxial cable 102 till thedistal most portion of antenna 104 is about 3.8 cm. This simulates thedistortion that antenna 104 experiences by the fundus during actualclinical use in endometrial ablation. The configuration shown in FIG.14V is the working configuration of antenna 104 in which antenna 104 canbe used for endometrial ablation. Thus several embodiments of antenna104 herein are capable of existing in 3 configurations: a firstconfiguration in which antenna 104 is laterally compressed for insertionthrough a lumen or opening, a second configuration in which antenna 104is longitudinally un-constrained and laterally un-collapsed in theabsence of significant external distorting forces on antenna 104 and athird configuration in which antenna 104 is longitudinally constrainedand laterally un-collapsed in the presence of external distorting forceson antenna 104. The third configuration is the actual workingconfiguration.

FIG. 14W shows the placement of the microwave antenna of FIGS. 14U and14V in a folded piece of tissue. In FIG. 14W, a slab of porcine muscletissue maintained at 37 degrees C. was folded over once. The cavityenclosed by the tissue fold approximately simulates the uterine cavity.Thereafter, antenna 104 of FIGS. 14U and 14V was inserted to asufficient depth such that the distal most region of antenna 104 isdistorted by the porcine tissue to achieve the working configuration asshown in FIG. 14V. Thereafter, the porcine tissue was ablated. Theablation was done for 90 s with a delivery of 40 W of microwave powerfrom a microwave generator at 0.915 GHz. Although in this experiment, aconstant power of 40 W was used throughout the ablation procedure; inclinical use the magnitude of power delivery by the microwave generatormay not be constant throughout the ablation procedure.

If we assume that about 85% of the total microwave energy delivered bythe microwave generator is ultimately delivered by antenna 104 totissue, the total energy delivered to tissue is about 3,000 Joules.Since the tissue used in FIG. 14W is designed to simulate uterineendometrial tissue, endometrial ablation protocols may be designed thatinvolve the delivery of about 3,000 Joules of microwave energy to theendometrium. Further, protocols of endometrial ablation may be designedthat deliver less than 3,000 Joules of microwave energy to theendometrium. This can be done for example, by pre-treatment of theuterus, by scheduling the patient for the ablation just after she has amenstrual period, etc.

In FIG. 14V, the total area of generally flattened antenna 104 in itsworking configuration is about 6.7 square centimeters. Thus, themicrowave energy delivered by antenna 104 is delivered to two oppositetissue surfaces, each measuring about 6.7 square centimeters. Again, ifwe assume that about 85% of the total microwave energy delivered by themicrowave generator is ultimately delivered by antenna 104 to tissue,the total power delivered to tissue is about 2.5 Watts per squarecentimeter of tissue. Further, protocols of endometrial ablation may bedesigned that achieve the desired clinical outcome while delivering lessthan 2.5 Watts of microwave power per square centimeter of endometrialsurface. This can be done for example, by hormonal pre-treatment of theuterus, by a mechanical pre-treatment of the uterus by D&C, byscheduling the patient for the ablation just after she has a menstrualperiod, etc.

FIG. 14X shows the unfolded piece of tissue of FIG. 14W showing theplacement of the microwave antenna of FIGS. 14U and 14V in alongitudinally constrained and longitudinally collapsed workingconfiguration and the ablation obtained from the microwave antenna. Itshould be noted that the ablation is roughly triangular in shape. Suchan ablation in the uterus is capable of ablating the entire uterineendometrium to treat menorrhagia.

FIG. 14Y shows an unfolded view of ablated tissue after the ablationshown in FIG. 14W. FIG. 14Z shows a view of the ablated tissue slicedthrough the plane 14Z-14Z in FIG. 14Y. It is seen in FIG. 14Z, that theablation is uniform and spans the full thickness of the tissue. There isno charring noted anywhere. Thus a transmural ablation spanning the full7-9 mm depth of tissue has been created. FIG. 14AA shows a view of theablated tissue sliced through the plane 14AA-14AA in FIG. 14Y. Similarto FIG. 14Z, FIG. 14AA shows that the ablation is uniform and spans thefull thickness of the tissue. There is no charring noted anywhere. Thusa transmural ablation spanning the full 7-10 mm depth of tissue has beencreated. Further, it should be noted that the lesion is deeper in thecenter and shallower towards the periphery of the lesion. Such anablation is clinically desired since the thickness of the endometrium isgreater toward the center of the uterus and is lower in the cornualregions and towards the lower uterine region. Further, deeper lesionsmay be created if desired by using one or more of: increasing the powerdelivered by the microwave generator, increasing the ablation time,occluding the blood flow to the uterus by temporarily occluding theuterine arteries, etc. Further, shallower lesions may be created ifdesired by using one or more of: reducing the power delivered by themicrowave generator, reducing the ablation time, circulating a coolingagent in the anatomy, etc.

FIG. 15A shows a view of an antenna of a microwave ablation deviceoptimized for endometrial ablation that comprises a single radiatingelement and two shaping elements. In FIG. 15A, antenna 104 comprises anopen loop shaped radiating element 112 that lies roughly at the centerof antenna 104. Distal end 158 of radiating element 112 lies adjacent tothe distal end of transmission line 102. The distal end 158 of radiatingelement 112 points in the proximal direction. In one embodiment,radiating element 112 is a continuation of the inner conductor 108 ofcoaxial cable 102. At least a proximal portion of radiating element 112is covered with an antenna dielectric 116 such as dielectric 110 ofcoaxial cable 102. The total length of radiating element 112 is about110+/−20 mm or about three quarters of the effective wavelength at 915MHz. In one embodiment, an antenna dielectric 116 may be located at thedistal end of transmission line 102. This antenna dielectric 116 mayenvelop the proximal portion of radiating element 112, the distal end158 of radiating element 112, and the proximal portions of loopedshaping elements 114. In addition to locally modifying the dielectricproperties of antenna 104, this antenna dielectric 116 may also be usedto mechanically hold together various portions of antenna 104. Theamount of antenna dielectric on radiating element 112 can be controlledfor tuning antenna 104 and shaping the microwave field profile generatedby antenna 104. Antenna 104 further comprises two shaping elements 114located on either side of radiating element 112 as shown. In oneembodiment, two shaping elements 114 are formed by two lengths ofconductive wires covered with an antenna dielectric 116. The proximalend of each of two shaping elements 114 is conductively connected toouter conductor 106 of coaxial cable 102. In one embodiment, the lengthof each shaping element 114 is about 110+/−20 mm or about three quartersof the effective wavelength at 915 MHz. The distal ends of each shapingelement 114 are joined together such that they form a common segment asshown in FIG. 15A. The microwave field emitted from radiating element112 interacts with and is shaped or redistributed by two shapingelements 114. This in turn increases the size of the generated lesion.The microwave field profile is substantially confined to the regions ofradiating element 112 and two shaping elements 114 without substantiallyextending to coaxial cable 102. The coaxial cable 102 in the embodimentin FIG. 15A herein is IW70 coaxial cable from Insulated Wire, Danbury,Conn. The inner conductor in this cable is Ag plated Cu with an OD of0.018 inches. The outer conductor is made of Ag plated Cu. The outermostlayer is a Teflon jacket. The total OD of the coaxial cable is 0.068inches. This IW70 cable is used as an example only. Several othercoaxial cables or other microwave transmission lines can be used toconstruct any of the devices herein. In any of the embodiments disclosedherein, coaxial cable 102 may comprise an inner conductor 108 made of aNitinol wire having an outer cladding or plating made of Ag, Au, Pt orany other highly conductive metal. Examples of methods that can be usedto add the outer layer on the Nitinol wire include, but are not limitedto: electroplating, electro-deposition or cladding. In one embodiment,the design of the remaining elements of coaxial cable 102 (dielectric110, outer conductor 106 and outer jacket 118) is the same as in theIW70 cable. The Nitinol wire may have shape-memory or super-elasticproperties. In one embodiment, one or more portions of the Nitinol wireare heat-shaped in a desired geometry.

FIG. 15B shows the placement of the antenna of FIG. 15A between twoopposite tissue surfaces for an ablation procedure and the resultingablation pattern that is obtained. In FIG. 15B two opposing slices ofporcine muscle tissue at 37 C were used to demonstrate the ablationprofile. To create the lesion in FIG. 15B, ablation power was deliveredfrom a 0.915 MHz microwave generator at 90-100 W and the ablation timewas 60 s. FIG. 15B shows a substantially uniform ablation withoutcharring that simulates an endometrial ablation.

FIG. 15C shows the reverse surfaces of the tissues of FIG. 15Bdemonstrating trans-mural lesions. Further, FIG. 15C shows that thereare no gaps in the lesion pattern. Further, the lesion depth tapers offtowards the edges of the lesion. Thus antenna 104 is capable of ablatinguterine endometrium such that the resulting lesion is deeper in thecenter of the uterus and shallower in the cornual and lower uterineregions.

FIG. 15D shows a view of an embodiment of an antenna that comprises asingle radiating element and two shaping elements. In this embodiment, alooped radiating element 112 emerges from the distal end of transmissionline 102. The proximal portion of radiating element 112 is covered withan antenna dielectric 116 as shown. The distal end of radiating element112 is also enclosed within the antenna dielectric 116. Two shapingelements 114 are located on symmetrically on either side of radiatingelement 112. The proximal ends of the two shaping elements 114 areelectrically connected to the distal end of a portion of thetransmission line (e.g. the outer conductor of a coaxial cable 102). Thefree ends of shaping elements 114 point in the proximal direction andare located within the antenna dielectric 116. The free ends of shapingelements 114 are in electrical conduction with each other and areelectrically insulated from portions of radiating element 112. Inaddition to locally modifying the dielectric properties of antenna 104,this antenna dielectric 116 may also be used to mechanically holdtogether various portions of antenna 104.

FIG. 15E shows a view of an embodiment of an antenna that comprises asingle radiating element and two shaping elements. The embodiment ofantenna 104 in FIG. 15E is similar to the embodiment of antenna 104 inFIG. 15D. However, in this embodiment, the proximal ends of shapingelements 114 are electrically connected to a portion of the transmissionline (e.g. the outer conductor of a coaxial cable 102) that is locatedproximal to the distal end of the transmission lien 102.

FIG. 15F shows a view of an embodiment of an antenna that comprises asingle radiating element and a single shaping element. In thisembodiment, radiating element 112 emerges distally from the distal endof transmission line 102. One end of shaping element 114 is mechanicallyconnected to the distal end of transmission line 102. Radiating element112 and shaping element 114 cross each other and are connected toregions of transmission line 102 proximal to the distal end oftransmission line 102. Radiating element 112 is mechanically,non-conductively connected to a region of transmission line 102 proximalto the distal end of transmission line 102. Whereas shaping element 114is electrically connected to a region of transmission line 102 proximalto the distal end of transmission line 102. Radiating element 112 may becovered with an antenna dielectric 116. A part of the microwave field inthis case lies proximal to the distal end of transmission line 102. Thelength of one or both of radiating element 112 and shaping element 114may be about three quarters of the effective wavelength of the microwaveenergy.

FIG. 15G shows a view of an embodiment of an antenna that comprises asingle radiating element and two shaping elements. The design of antenna104 in FIG. 15G is similar to antenna 104 in FIG. 15A. However, in theembodiment in FIG. 15G, two shaping elements 114 are not joined to eachother. Further, the distal ends of two shaping elements 114 terminate atpoints that are more distal than the corresponding termination points onantenna 104 in FIG. 15A. Also, in FIG. 15G, a layer of antennadielectric 116 may be used to cover the junction region between antenna104 and transmission line 102. In an alternate embodiment, the lengthsof shaping elements 114 in FIG. 15G may be longer than three quarters ofthe effective wavelength of the microwave energy.

FIG. 15H shows a view of an embodiment of an antenna that comprises asingle radiating element and two shaping elements. In this embodiment,radiating element 112 is similar to radiating element 112 of FIG. 15A. Afirst shaping element 114 is a closed loop and is located aroundradiating element 112 as shown. Both ends of the closed loop areelectrically connected to a portion of the distal end of transmissionline 102. Antenna 104 further comprises a linear shaping element 114arranged parallel to the distal end of transmission line and located atthe center of antenna 104. Linear shaping element 114 is alsoelectrically connected to a portion of the distal end of transmissionline 102. The distal end of linear shaping element 114 terminatesproximally to the distal most portion of antenna 104.

FIG. 15I shows a view of an embodiment of an antenna that comprises asingle radiating element and a single shaping element. In thisembodiment, radiating element 112 is similar to radiating element 112 ofFIG. 15A. Shaping element 114 is heart shaped and is located aroundradiating element 112 as shown. Shaping element 114 is electricallyconnected to a portion of the distal end of transmission line 102.

FIG. 15J shows a view of an embodiment of an antenna that comprisesmultiple radiating elements and multiple shaping elements. Multipleshaping elements 114 are electrically connected to a portion of thetransmission line 102. Some or all of multiple radiating elements 112may be covered with antenna dielectric 116. Multiple radiating elements112 and multiple shaping elements 114 are placed in alternating fashionto enhance microwave field interaction coupling between multipleradiating elements 112 and multiple shaping elements 114. Although theembodiment shows 4 radiating element 112 and 3 shaping elements 114,alternate embodiments are possible comprising between 2-64 radiatingelements 112 and between 2-64 shaping elements 114.

FIG. 15K shows a view of an embodiment of an antenna that comprises asingle radiating element and a spirally shaped shaping element. Antenna104 comprises a looped radiating element 112. An antenna dielectric 116covers at least the distal end of radiating element 112. The length ofradiating element 112 may be three quarters of the effective wavelengthof the microwave energy. Spirally arranged shaping element 114 may be acontinuation of outer conductor of a coaxial cable 102 or may be aconductive element electrically connected to a shielding element of atransmission line 102.

FIG. 15L shows a view of an embodiment of an antenna that comprises asingle radiating element and two shaping elements. In FIG. 15L, a loopedradiating element 112 having a distal end 158 is positioned roughly atthe center of the axis of antenna 104. Looped radiating element 112 maybe formed by an extension of inner conductor of coaxial cable 102 andmay be covered with antenna dielectric 116. The length of radiatingelement 112 may be three quarters of the effective wavelength of themicrowave energy. In the embodiment shown, two shaping elements 114 arenon-identical and are arranged on either side of radiating element 112.In one embodiment, two shaping elements 114 are formed by an extensionof an outer conductor of coaxial cable 102. In an alternate embodiment,shaping elements 114 may be identical and symmetrically arranged oneither side of radiating element 112.

FIG. 15M shows a view of an embodiment of an antenna that comprises asingle radiating element and a loop shaped shaping element. In FIG. 15M,radiating element 112 may be similar in design to a monopole antenna. Inone embodiment, the proximal side of looped radiating element 114 may beformed by formed by an extension of the outer conductor of the coaxialcable 102. The distal side of looped radiating element 114 may be formedby an elongate conductor that is attached to the extension of the outerconductor of the coaxial cable 102 to complete the loop. In an alternateembodiment, a single conductor may be used to form looped shapingelement 114. The proximal ends of looped shaping element 114 areelectrically connected to the shielding element of the transmission line102.

FIG. 15N shows a view of an embodiment of an antenna that comprises asingle radiating element and two shaping elements. In FIG. 15L, aradiating element 112 having a distal end 158 is in a wavy or zig-zagconfiguration and is positioned roughly at the center of antenna 104.Radiating element 112 may be formed by an extension of inner conductorof coaxial cable 102 and may be covered with antenna dielectric 116. Thelength of radiating element 112 may be three quarters of the effectivewavelength of the microwave energy. The width of the configuration ofradiating element 112 gradually increases in the distal direction. Inthe embodiment shown, two shaping elements 114 are arranged on eitherside of radiating element 112.

FIGS. 15O-15Q show embodiments of antenna 104 comprising mechanisms toensure proper deployment of antenna 104 in the anatomy. In FIG. 15O, oneor both of radiating element 112 and shaping element 114 are made ofshape memory or super-elastic materials such as Nitinol. Antenna 104comprises a radiating element 112 covered with antenna dielectric 116.Radiating element 112 emerges at an angle to distal end of transmissionline 102. Radiating element 112 is deployed in a bent shape as shown inFIG. 15O. Shaping element 114 is electrically connected to the shieldingelement of transmission line 102. Shaping element 114 is deployed in abent shape as shown in FIG. 15Q. The length of one or both of radiatingelement 112 and shaping element 114 may be about three quarters of theeffective wavelength of the microwave energy. The shape memory orsuper-elastic properties of antenna 104 enable proper deployment ofantenna 104 in the anatomy. The design of antenna 104 in FIG. 15P issubstantially similar to antenna 104 in FIG. 15O. However, in FIG. 15P,antenna 104 may or may not be made of shape memory or super-elasticmaterials. Antenna 104 in FIG. 15P is embedded in a substantially planarregion of a rigid or flexible antenna dielectric 116. Antenna dielectric116 fixes the relative positions of radiating element 112 and shapingelement 114 thereby ensuring proper deployment in the anatomy. Thedesign of antenna 104 in FIG. 15Q is substantially similar to antenna104 in FIG. 15O. However, in FIG. 15Q, antenna 104 may or may not bemade of shape memory or super-elastic materials. Antenna 104 in FIG. 15Pcomprises one or more rigid or flexible antenna dielectrics 116 in theform of struts or connection elements connecting radiating element 112and shaping element 114. Antenna dielectric 116 struts or connectionelements fix the relative positions of radiating element 112 and shapingelement 114 thereby ensuring proper deployment in the anatomy.

In a method embodiment, a user is provided with antennas 104 of 2 sizes.The user can select the appropriately sized antenna 104 based on apre-procedure evaluation. In one embodiment, the two antennas are scaledversions of each other. In another embodiment, not all elements of theantenna 104 are scaled up or down in the same proportion. For example,ratio of the thicknesses of the dielectric on the radiating elements 112may or may not be the same as the ratio of the sizes of radiatingelements 112. The materials of construction of elements of the twoantennas 104 may be same or different. Additional elements may be addedon one or more of the different sized antennas 104. The larger antenna104 may be used to treat target tissue lying in a certain larger sizerange and the smaller antenna 104 may be used to treat target tissuelying in a certain smaller size range. The two size ranges may overlapor be non-overlapping. The usage parameters (e.g. energy delivery time,energy delivery power, etc.) during the use of the devices may be sameor different. The formulas used for calculating the usage parameters maybe same or different.

In one method embodiment, the duty cycle of microwave power deliveryvaries during the course of an ablation. In one such embodiment, duringan initial stage of an ablation, microwave power is delivered at ahigher duty cycle and during a later stage of the ablation, microwavepower is delivered at a lower duty cycle. In one such embodiment,microwave power is delivered continuously (i.e. at 100% duty cycle)during the initial phase of an ablation to raise the temperature oftarget tissue to a desired level or within a desired temperature range.Thereafter, microwave power is delivered at less than 100% duty cycle tomaintain the temperature of target tissue at the desired level or withinthe desired temperature range for a desired period of time. In oneembodiment, the desired level of temperature of target tissue is 55-75C. In one embodiment, the change in microwave duty cycle is performedbased on a temperature feedback. In one embodiment, the change inmicrowave duty cycle is performed automatically by a microwave generatorafter a pre-programmed time.

The microwave duty cycle may be changed automatically by a microwavegenerator based on input data of pulsatile flow of blood. In oneexample, during higher blood flow, a higher duty cycle may be used andduring lower blood flow, a lower duty cycle may be used. This will avoidexcessive energy delivery. In another example, during lower blood flow,a higher duty cycle may be used. This may be used for example, toachieve a greater amount of ablation. In one embodiment, the system isprogrammed to deliver a therapy that uses temperature feedback to adjustthe duty cycle during the therapy. Such manipulation of the duty cycleof microwave power deliver may be used in any of the treatmentsdisclosed herein including, but not limited to: microwave endometrialablation, ablation of portion of the heart, ablation of vascular tissue,etc.

Similar method and device embodiments are envisioned wherein themagnitude of microwave power delivered to tissue is varied instead ofvarying the duty cycle. That is an increased microwave power isdelivered instead of increasing the duty cycle and a reduced microwavepower is delivered instead of reducing the duty cycle.

A treatment assembly comprising a microwave antenna and one or moresteerable or non-steerable catheters may be introduced via atrans-esophageal approach into the esophagus. Thereafter, the treatmentassembly may used to ablate an abnormal esophageal surface layer to cureBarrett's Esophagus. A treatment assembly comprising a microwave antennaand one or more steerable or non-steerable catheters may be introducedvia a trans-cervical approach into the uterine cavity to ablate theuterine endometrium or other tissues of the uterine wall. An ultrasoundimaging device may be used to visualize the anatomy and/or the treatmentassembly. The treatment assemblies may be used to orient antenna 104perpendicularly or parallel to the longitudinal axis of anatomicallumens. Antenna 104 may be moved relative to the longitudinal axis ofthe anatomical lumens or cavities. For example, antenna 104 may berotated or translated relative to the longitudinal axis to positionantenna 104 at various locations in the anatomical lumens or cavities.Such motions of antenna 104 may be used to position antenna 104 toablate or otherwise treat the entire cavity or lumen wall or an entirecircumferential region of the cavity or lumen wall.

Helical antenna 104 configurations such as shown in FIG. 3D areespecially suited to contact the internal lining of one or moreanatomical cavities of lumens. In addition to other movements disclosedherein, the outer diameter and/or length of the helical shaped antenna104 may be changed to obtain better contact with target tissue. Forexample, the outer diameter of helical antenna 104 in FIG. 3D may beincreased to increase the force exerted on the surrounding tissue byantenna 104. In a particular embodiment, a helical antenna 104 is usedto heat one or more regions of a target vein for treating venous refluxdisease. A helical configuration of antenna 104 may be created by one ormore of: introducing antenna 104 in a helical introducing catheter ortube, having a pre-shaped helical antenna 104, twisting a sufficientlyrigid device attached to a portion of antenna 104, and pulling orpushing a sufficiently rigid device attached to a portion of antenna104.

Any of the ablation devices 100 disclosed herein or an introducingcatheter or sheath used to introduce an ablation device 100 may comprisea fluid transport lumen. The fluid transport lumen may extend from aproximal region of ablation device 100 or the introducing catheter orsheath till a distal region of ablation device 100 or the introducingcatheter or sheath that is placed inside the patient's body. The fluidtransport lumen may be used for one or more of: evacuating liquids orgases from the anatomy; introducing liquids inside the body such asanesthetics, contrast agents, cauterizing agents, alcohols, thermalcooling agents, a fluid dielectric medium that surrounds antenna 104,antibiotics and other drugs, saline and flushing solutions; introducinggases inside the body such as carbon dioxide for distending a cavity(e.g. the uterine or peritoneal cavity) or detecting perforation of acavity; applying suction to collapse a tissue region around the antenna104. Suction may be applied inside a cavity (e.g. the uterine cavity) toincrease the contact of antenna 104 with lining of the cavity. When agas such as carbon dioxide is used for distending the uterine cavityand/or for detecting perforation of the uterus, the gas may be deliveredat a pressure between 20-200 mmHg.

Any of the devices disclosed herein including any ablation device 100disclosed herein may comprise a device transport lumen. The devicetransport lumen may extend from a proximal region of ablation device 100till a distal region of ablation device 100 that is placed at a desiredlocation in the patient's body. The device transport lumen may be usedfor one or more of: introducing one or more elongate diagnostic and/ortherapeutic devices in the body, introducing ablation device 100 over aguidewire or other introducing device and introducing an imaging orvisualization device.

Any of the devices disclosed herein may comprise a cooling modality tocool one or more regions of the device. For example, a device maycomprise a cooling jacket or another cooling modality to cool one ormore of: a surface of the device, a shaft of the device and an antennaof the device.

Any of the devices disclosed herein may comprise one or more of: animpedance measuring modality, a temperature measuring modality and anelectrophysiological signal measuring modality. In one embodiment, adevice disclosed herein comprises a radiometric temperature sensingmodality. This radiometric temperature sensing modality may be used tonon-invasively measure of temperature at the surface or at a deeperregion of tissue. This in turn can be used to obtain real-time feedbackabout the effectiveness of energy delivery by the device.

Any of the antennas 104 disclosed herein may comprise additionaldeployment features used to convert an antenna 104 from a non-workingconfiguration wherein antenna 104 is incapable of or sub-optimallycapable of performing the desired function to a working configurationwherein antenna 104 is capable of performing a desired function. In oneembodiment, a pull wire may be used to pull one or more regions ofantenna 104 to change the shape of antenna 104 from a non-workingconfiguration to a working configuration. In another embodiment, asufficiently rigid shaft comprising a coaxial cable 102 may be used topush one or more regions of antenna 104 against tissue to change theshape of antenna 104 from a non-working configuration to a workingconfiguration.

Any of the antennas 104 disclosed herein may comprise or be used incombination with a microwave shielding or absorbing element. Themicrowave shielding or absorbing element may shield a majority of or apart of the microwave field emitted by antenna 104. Examples ofmicrowave shielding or absorbing elements include, but are not limitedto: inflatable or non-inflatable balloons, hollow structures filled withair or a circulating or non-circulating fluid, metallic wires or meshes,metallic films or other flattened structures, gels or other conformablestructures, structures filled or wetted with water, structures designedto circulate one or more fluids on the surface of antenna 104, coolingmodalities and mechanical spacers made of dielectric materials. In aparticular embodiment, the microwave shielding or absorbing element isdisc-shaped. In another embodiment, the microwave shielding or absorbingelement is slidably positioned relative to radiating element 112. Inthis embodiment, the shape of microwave field emitted by antenna 104 maybe changed by sliding the microwave shielding or absorbing elementrelative to radiating element 112. In one such embodiment, a tubularmicrowave shielding or absorbing element surrounds a substantiallylinear antenna 104. The length of the microwave field shape and theresulting lesion length by antenna 104 may be changed by sliding themicrowave shielding or absorbing element relative to antenna 104. Suchmicrowave shielding or absorbing elements in combination with an antenna104 disclosed herein may be used to ablate a local region of tissue(e.g. a part of the uterine endometrium or a vascular endothelium) or toablate only a single surface of the tissue (e.g. a single surface of theuterine endometrium).

Any of the antennas 104 disclosed herein may comprise or be used incombination with a constraining element that not only shapes themicrowave field profile of antenna 104 also mechanically shapes antenna104. Antenna 104 may be mechanically constrained by constraining element146 before insertion near or into the target tissue. The concept ofconstraining antenna 104 in an introducing catheter or sheath has beenpreviously disclosed. FIGS. 16A-16D show various views of an embodimentof a constraining element 146 that is usable for constraining antenna104 to change or constrain the shape of antenna 104. In one embodiment,constraining element 146 comprises a substantially rectangular cavity ordepression 166 or a chamber, gap, hole or pocket designed to constrainantenna 104 in a more rectangular shape. Such a constrained antenna 104may be used for deep or surface ablation of tissue. In one embodiment, aconstrained antenna 104 is used to ablate soft tissue by placing antenna104 between the target tissue and constraining element 146. Constrainingelement 146 may be used as a shield to protect collateral tissue damageby preventing any ablation on the side of antenna 104 opposite to targettissue. Constraining element 146 may comprise one or more metallicelements for microwave shielding. Constraining element 146 may be madefrom suitable dielectric materials including, but not limited to PTFE,EPTFE, silicone and ABS. In another embodiment, a constrained antenna104 is used inside the abdominal cavity to ablate an abdominal organ. Aconstrained antenna 104 may be used to ablate a surface of an organ e.g.the outer surface of the organ. FIG. 16A shows a view of a combinationof constraining element 146 along with ablation device 100 positioned inthe constraining element 146 such that antenna 104 is constrained inrectangular cavity or depression 166. In the embodiment in FIG. 16A,antenna 104 comprises a radiating element 112 and a shaping element 114that is in electrical contact with outer conductor of coaxial cable 102.Antenna 104 is enclosed in a constraining element 146 that mechanicallyconstrains antenna 104. FIG. 16B shows a perspective view ofconstraining element 146 comprising a cavity or depression 166 usable tomechanically shape antenna 104. FIG. 16C is a side view of constrainingelement 146 of FIG. 16B showing cavity or depression 166. FIG. 16D showsa view of the crossection of constraining element 146 through plane16D-16D. Embodiments of constraining elements 146 may be combined withany of the antenna 104 embodiments disclosed herein to reduce themicrowave field intensity on one side of antenna 104.

Any of the devices and elements disclosed herein may be controlled byrobotic control. Further, any of the devices disclosed herein may beintroduced and/or navigated and/or operated using a robotic system.Examples of such robotic systems include, but are not limited to theSensei™ Robotic Catheter System made by Hansen Medical, Inc. and the daVinci® Surgical System made by Intuitive Surgical, Inc. For example, anyintroducing sheath used to introduce an antenna 104 may be a roboticcatheter with an introducing lumen.

Any of the devices disclosed herein may be introduced and/or manipulatedthrough one or more lumens of one or more elongate sheaths or catheters.Several such treatment assemblies comprising an ablation device and oneor more elongate sheaths or catheters are possible. For Example, atreatment assembly comprising an ablation device 100 slidably positionedin a lumen of an introducing sheath may be designed. One or more of suchintroducing sheaths or catheters can comprise one or more steeringmechanisms. Examples of such steering mechanisms include, but are notlimited to pull wires, pre-shaped tubular sheaths or stylet structures.

Any of the devices disclosed herein may have a varying degree offlexibility along the length of the device or antenna 104.

In those cases where a device requires connection to an auxiliarycomponent (e.g., a power supply, imaging monitor, fluid source, etc.) ahandle of the device can include the desired means for connection.

Any of the cardiac diagnostic or treatment procedures disclosed hereinmay include the use of a pericardial device placed in the pericardialspace or around the epicardium. The pericardial device may be insertedby a sub-xiphoid approach. Such devices may be used for one or more of:preventing excessive ablation, confirming trans-mural nature of anablation, cooling the surrounding anatomy, preventing unwanted damage tothe phrenic nerve or to the esophagus, etc. In one such embodiment, anICE (intra-cardiac echocardiography) probe may be inserted into thepericardial space or around the epicardium. The ICE probe may be used tovisualize one or more device and/or one or more anatomical regions. Inanother embodiment, a deflectable device is inserted into thepericardial space or around the epicardium. The device is deflected orotherwise manipulated to create a space or increase the distance betweenthe posterior aspect of the heart and the esophagus. This may be used toincrease the safety of cardiac ablation procedures. In anotherembodiment, an esophagus protecting device is inserted in thepericardial space or around the epicardium such that the device ispositioned between the posterior aspect of the heart and the esophagus.Such a device may be used to prevent esophageal injury during cardiacablation procedure. Examples of such devices include, but are notlimited to: inflatable devices, spacing device, devices with coolingmechanisms, etc. In one embodiment, a mapping catheter comprising one ormore electrodes adapted for electrophysiological mapping is inserted inthe pericardial space or around the epicardium. The mapping catheter maybe used for measuring electrophysiological signals from cardiac tissue.In one embodiment, the mapping catheter is used for confirmingtrans-mural nature of a lesion. In one embodiment, the mapping cathetermay be used to map the activation patterns of electrophysiologicalsignals in cardiac tissue. In one embodiment, the pericardial device isa hollow catheter to deliver one or more fluids in the anatomy. Any ofthe fluids mentioned herein may be delivered by such catheters. In oneembodiment, the pericardial device comprises an antenna printed on aflat substrate as shown in FIG. 5A. In one embodiment, the pericardialdevice comprises an ablation modality (e.g. a microwave antenna, RFelectrodes, etc.) to ablate one or more cardiac regions to treat one ormore of: atrial fibrillation, ventricular tachycardia, atrial flutterand other arrhythmias. The pericardial device may be used to deploynavigation markers used in 3-D surgical electro-anatomical navigationsystems in the pericardial space or around the epicardium. Examples ofsystems that use such navigation markers include, but are not limitedto: Carto navigation system (Biosense-Webster, Diamond Bar, Calif.) andthe EnSite NavX system (St. Jude Medical, St. Paul, Minn.). In oneembodiment, the pericardial device is a hollow catheter that is used tointroduce multiple mapping catheters. Each of the mapping catheters mayhave a tether. The tethers of each of the multiple mapping catheters maybe folded back into the hollow catheter.

In any of the method embodiments herein, pre-procedure anatomical datamay be obtained by imaging the anatomy. This anatomical data may be usedto tailor a method for the particular patient. In one embodiment, theanatomical data is used to adjust a size or shape parameter of ablationdevice 100. In another embodiment, the anatomical data is used todetermine a treatment parameter e.g. ablation power, ablation time, etc.The anatomical data may be obtained by one or more of: ultrasoundimaging with or without contrast agent, fluoroscopic or X-ray imagingwith or without a contrast agent, MRI with or without a contrast agent,PET scan, endoscopy and using a mechanical size determining devices(e.g. a uterine sound, an elongated device with distance markings,etc.).

Ablation device 100 disclosed herein may be inserted and/or used blindlyi.e. without using any additional imaging modality.

Ablation device 100 disclosed herein may be inserted and/or used underendoscopic (e.g. using hysteroscopy, cystoscopy, endoscopy, laparoscopy,flexible endoscopy, etc.) guidance.

Ablation device 100 disclosed herein may be inserted and/or used underultrasonic guidance.

Ablation device 100 disclosed herein may be inserted and/or used underradiological guidance. In one embodiment, ablation device 100 is usedunder X-ray or fluoroscopic guidance. Ablation device 100 may compriseone or more radiopaque markers to enable the visualization of one ormore regions of ablation device 100 under X-ray or fluoroscopicguidance.

Ablation device 100 may comprise a visualization modality or means forcoupling to a visualization modality. In one embodiment, thevisualization modality (e.g. fiberoptic fibers or other optical imagingmodality, ultrasound catheter, etc.) may be embedded in a wall ofablation device 100 and/or an introducing catheter 148. In anotherembodiment the visualization modality (e.g. fiberoptic fibers or otheroptical imaging modality, ultrasound catheter, etc.) may be introducedthrough a lumen of ablation device 100 or introducing catheter 148.

Ablation device 100 may comprise one or more gas or liquid inflatableballoons for doing one or more of: positioning antenna 104, providing acooling modality, enabling better contact of antenna 104 with targettissue and deploying antenna 104.

Even though a majority of the disclosure uses a coaxial cable as anexample of a transmission line, an alternate transmission lines fortransmitting microwaves may be used. Examples of such alternatetransmission lines for transmitting microwaves include, but are notlimited to: waveguides, microstrip lines, strip lines, coplanarwaveguides and rectax. In such embodiments, the shaping element(s) 114may be in electrical conduction with the shielding element of thetransmission line. For example, in a strip line, wherein the shieldingelement is the combination of the two ground planes, shaping element(s)114 may be in electrical conduction with the combination of the twoground planes. For example, in a hollow metallic waveguide, wherein theshielding element is the electrically conducting wall, shapingelement(s) 114 may be in electrical conduction with the electricallyconducting wall.

One or more elements described herein may comprise one or moreadditional treatment modalities. Examples of such additional treatmentmodalities include, but are not limited to: radiofrequency electrodesincluding radiofrequency ablation electrodes, heating elements,cryotherapy elements, elements for emitting laser and other radiation,elements for introducing one or more fluids, etc. For example, radiatingelement 112 and/or shaping element 114 may comprise multipleradiofrequency ablation electrodes. Such radiofrequency ablationelectrodes enable the use of the devices disclosed herein in conjunctionwith other modalities such as radiofrequency ablation. One or moreelements described herein may comprise one or more additional diagnosticmodalities. Examples of such diagnostic modalities include, but are notlimited to: temperature sensors, impedance sensors, electrophysiologicalsignal sensors, visualization elements, etc. For example, radiatingelement 112 and/or shaping element 114 may comprise multiple temperaturesensors.

One or more devices disclosed herein may comprise one or more lubriciouscoatings. One or more devices disclosed herein may comprise one or moreregions that are thermally insulated to protect non-target tissue.

Even though antenna 104 is designed to work well without exact contactwith tissue, there may be an advantage if the proper positioning of theantenna 104 is determined just before the ablation. For example, ifantenna 104 is not deployed in the preferred working configuration, thelesion may not be therapeutically optimal. The invention herein furtherincludes a non-visual and integrated device that can be used todetermine the proper positioning of antenna 104 just before theablation. The method uses reflectometry to determine the properpositioning. If the antenna is not properly positioned, the antenna maynot be well matched. In such a case, the measured reflected power for aparticular range of incident power (the power sent to the antenna) willnot be within a normal range. Thus by measuring if the reflected poweris within a normal range, we can say whether the antenna is properlypositioned. An example of such a procedure is as follows. 1. Conduct aseries of experiments with the antenna properly positioned in the targettissue, 2. Measure the reflected power level in all the experiments fora particular range of incident power level with the antenna properlypositioned in the target tissue, 3. Determine a “normal range” ofreflected power level that is to be expected if the antenna is properlypositioned in the target tissue, 4. During the endometrial ablationprocedure, measure the reflected power level, 5. If the reflected powerlevel is within the normal range, conclude that the antenna is properlypositioned. If the reflected power level is not within the normal range,conclude that the antenna is not properly positioned. As an optionalextra step, a series of experiments may be conducted with the antennaimproperly positioned in the target tissue by having the antennadeployed purposely in imperfect or wrong configuration. This is todetermine an “abnormal range” of incident power level that is to beexpected if the antenna is not properly positioned in the target tissue.

The reflected power level can be measured by 1. using an external powermeter or 2. using a power meter that is in-built within the microwavegenerator.

Various additional embodiments of antenna 104 may be designed whereinradiating element 112 is a straight or curved or bent or pre-shapedmonopole antenna.

In any of the method embodiments herein, the lesion size may be deepenedor lengthened or widened by one or more of: increasing the powerdelivered by the microwave generator, increasing the ablation time,temporary reducing the blood flow to the anatomy, pre-treating theanatomy, etc. Further, the lesion size may be made shallower or shorteror narrower by one or more of: reducing the power delivered by themicrowave generator, reducing the ablation time, circulating a coolingagent in the anatomy, pre-treating the anatomy, etc.

The microwave field generated by any antenna 104 disclosed herein may bedirected towards a particular direction by a variety of mechanisms. Forexample, a microwave reflector (e.g. a metallic mesh) may be positionedon one side of a flat or planar ablation portion to generate highermicrowave energy intensity on the other side of the flat or planarablation portion. One or more microwave absorbing or shielding orreflecting materials may be used in combination with the embodimentsdisclosed herein to direct the microwave field to a particulardirection. In one embodiment, the whole or part of shaping element 114is designed to act as a microwave shield or reflector or absorber.

Devices disclosed herein may be constructed with various orientations ofthe antenna 104 relative to the region of coaxial cable 102 immediatelyproximal to antenna 104. For example, devices herein may be designedwith an antenna 104 that is substantially parallel to or in the plane ofthe region of coaxial cable 102 immediately proximal to antenna 104.Devices can also be designed with an antenna 104 oriented at an angle(e.g. 90+/−20 degrees, 45+/−20 degrees) to the region of coaxial cable102 immediately proximal to antenna 104. This is advantageous to reachhard-to-reach target regions in the body. The relative orientation ofwhole or portions of antenna 104 relative to the device shaft (e.g. thecoaxial cable 102) may be fixed or changeable. For example, there may bea springy joint or region between antenna 104 and the shaft. In anotherembodiment, there may be an active steering mechanism e.g. a pull wiremechanism to change the relative orientation of whole or portions ofantenna 104 relative to the shaft. Such mechanisms may be used forproper positioning of antenna 104 on the target tissue or for navigatingthe device through the anatomy. For example, an antenna 104 deployedthrough an endoscope or through a laparoscope port may be deployed andnavigated such that antenna 104 lies in the plane of the target tissue.

The user may be supplied several devices of varying size and/or shape.The user may then select the proper device based on his judgment tocarry out the ablation. In a particular embodiment, 2 to 3 differentdevices with antennas 104 of similarly shape but different sizes aresupplied. The user then selects the proper device. Such multiple devicesmay be packaged separately or together. In another embodiment, 2 to 3different devices with antennas 104 of similar sizes but differentshapes are supplied. The user then selects the proper device as per theneed. In one method embodiment, the deployment of the device is tailoredto the particular target tissue or cavity. In such embodiments, whole orparts of antenna 104 are designed to be deployed in a particular sizeand/or shape that best fits the particular target tissue or cavity.

Several examples or embodiments of the invention have been discussedherein, but various modifications, additions and deletions may be madeto those examples and embodiments without departing from the intendedspirit and scope of the invention. Thus, any element, component, methodstep or attribute of one method or device embodiment may be incorporatedinto or used for another method or device embodiment, unless to do sowould render the resulting method or device embodiment unsuitable forits intended use. For example, several embodiments of ablation devices100 may be created by combining antenna 104 of one embodiment with adevice feature of another embodiment unless to do so would render theresulting device embodiment unsuitable for its intended use. Anysuitable antenna disclosed herein may be used to perform any of themethods disclosed herein. If the various steps of a method are disclosedin a particular order, the various steps may be carried out in any otherorder unless doing so would render the method embodiment unsuitable forits intended use. Various reasonable modifications, additions anddeletions of the described examples or embodiments are to be consideredequivalents of the described examples or embodiments.

We claim:
 1. A microwave energy delivery device for supplying energy from an energy source, the microwave energy delivery device comprising: a microwave antenna coupled to the energy source, the microwave antenna comprising a radiating element and a shaping element; the radiating element comprises a planar loop shape having a transverse section that deforms when advanced against tissue while remaining in the planer loop shape, the radiating element configured to emit a volumetric microwave field when energized by the energy source; and where the shaping element is electrically insulated from the radiating element and is positioned adjacent to the radiating element such that the shaping element alters a shape of the microwave field to be limited uniformly around the microwave antenna portion.
 2. The microwave energy delivery device of claim 1, where the microwave antenna comprises a profile selected from a group consisting of: a linear profile, a non-linear profile, a planar profile, and a 3 dimensional profile.
 3. The microwave energy delivery device of claim 1, where the microwave antenna is located at a distal end of a transmission line and the radiating element and the shaping member are located distal to the distal end of the transmission line.
 4. The microwave energy delivery device of claim 4, wherein the radiating element is continuous with a conductor of a transmission line coupled to the microwave antenna.
 5. The microwave energy delivery device of claim 4, where the shaping element is connected to the shielding element at or near the distal end of the transmission line.
 6. The microwave energy delivery device of claim 3, where the shaping element is located distal to the distal end of the transmission line.
 6. The microwave energy delivery device of claim 1, wherein the radiating element comprises a conductor selected from the group consisting of a non-linear conductor, a linear conductor, a helical conductor, and a planar conductor.
 6. The microwave energy delivery device of claim 1, wherein the radiating element comprises a conductor having a length that is an odd multiple of one quarter of the effective wavelength and where the wavelength is selected from a group consisting of 433 MHz ISM band, 915 MHz ISM band, 2.45 GHz ISM band and 5.8 GHz ISM band.
 7. The microwave energy delivery device of claim 1, where the shaping element comprises a profile selected from the group consisting of a linear profile, a non-linear profile, a planar profile, a 3 dimensional profile.
 8. The microwave energy delivery device of claim 1, where the radiating element and shaping element are parallel.
 9. The microwave energy delivery device of claim 1, where radiating element is planar and the shaping element is planar and the plane of radiating element is parallel to the plane of shaping member.
 10. The microwave energy delivery device of claim 1, where the shaping element improves a power efficiency of the antenna.
 11. The microwave energy delivery device of claim 1, where the shaping element improves the impedance matching of the device.
 12. The microwave energy delivery device of claim 1, where the shaping element improves the bandwidth over which the antenna delivers an acceptable performance.
 13. The microwave energy delivery device of claim 1, where the antenna further comprises a dielectric that covers one or both of: radiating element and shaping member and shapes the microwave field by changing the local dielectric environment in the region wherein antenna dielectric is located.
 14. The microwave energy delivery device of claim 16, where the antenna dielectric electrically insulates radiating element from the surrounding.
 15. The microwave energy delivery device of claim 1, where the microwave antenna generates a microwave field profile selected from the group consisting of: a radially symmetric microwave field profile and a bilaterally symmetric microwave field profile.
 16. The microwave energy delivery device of claim 1, wherein the antenna generates a microwave field profile that is wider distally and narrower proximally.
 17. The microwave energy delivery device of claim 1, where the microwave field extends volumetrically around the microwave antenna.
 18. The microwave energy delivery device of claim 1, where the shaping element is in direct or indirect electrical contact with the shielding element. 